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Hudson, Jessica --- "The Price of Coherence in Estoppels" [2017] SydLawRw 1; (2017) 39(1) Sydney Law Review 1


The Price of Coherence in Estoppels

Jessica Hudson[∗]

Abstract

Various reform proposals have been suggested in respect of common law estoppels and equitable estoppels in the pursuit of coherence between doctrine and norm. Before any decisive steps are taken, it is important to be sure of the true normative foundations informing common law estoppels. This article offers an alternative account of those foundations, with a view to arguing that within the realm of estoppels, coherence is best served by a rational separation of the categories of estoppels, rather than unification. Common law estoppels and equitable estoppels do not share a common purpose or themes upon which a unified doctrine of estoppel can be built. This article concludes by exploring the implications arising from maintenance of the division between the categories of estoppels, including the control mechanisms that limit the operation and effect of common law estoppels and, in particular, estoppels in pais.

I Introduction

Law should be coherent.[1] This article understands coherence[2] as the alignment between an individual doctrine of law and its underlying rationale(s).[3] Coherence in this sense has been alluded to by judges and scholars across the common law world with respect to estoppels.[4] The realm of estoppels has been understood as comprised of two distinct categories — common law estoppels and equitable estoppels — that are bounded by the line between representations of facts and promises.[5] Each category of estoppels differs in mode of operation and effect. The existence of these different types of estoppels has fuelled proposals for reform to achieve a unified doctrine of estoppel for the sake of coherence.[6] It has been suggested that some common law estoppels might be aligned with their equitable counterparts on the basis that these estoppels serve the same purpose of the prevention of detriment.[7] The idea being that the same end(s) should be achieved by the same means. This article urges caution in opposition to these proposed reforms.

In relation to one particular common law estoppel, estoppel by representation, the author has previously argued that such reforms would undermine the true purpose of that estoppel.[8] This article looks beyond estoppel by representation and considers the broader question whether coherence in estoppels is served by unification of some common law estoppels, including estoppel by representation, with equitable estoppels. The analysis draws on previous research as to the normative underpinnings of estoppel by representation to demonstrate that common law estoppels and equitable estoppels have different normative concerns. Contrary to the calls for merger, this article suggests that coherence may, in fact, be served by maintaining separate categories.

Assuming that reform on the basis of coherence is a valid objective,[9] it can only be possible where there is alignment of underlying norms and operational effect across the various estoppels targeted for unification. The point of this article is that such alignment does not exist, as common law estoppels and equitable estoppels do not share a common purpose or rationale upon which a unified doctrine of estoppel can be built. Relying on previous research in relation to estoppel by representation, the article argues that the targeted common law estoppels are concerned with preserving party autonomy by ensuring that a state of affairs adopted by A and B for the purposes of their legal relations is the state of affairs according to which the legal consequences of their relationship is determined in litigation. Equitable estoppels, on the other hand, are concerned with determining what are the substantive rights and obligations existing between the parties. The way that equitable estoppels answer this question is driven by the extent to which it would be unconscionable to allow one party, A, to depart from an assumption or expectation that A induced in B.

Arguments in favour of maintaining the division between common law estoppels and equitable estoppels have been made before.[10] However, a limit to some of these arguments is that they rely upon the existence of the differences between the categories of estoppels without providing a reason why the differences should be maintained. Just because one estoppel happens to be different from another does not mean that it should be so. The need to provide a normative account for the division between common law estoppels and equitable estoppels is all the more important in the face of judicial and academic opinion that regards the division as a historical quirk without any normative justification.[11] This article takes the argument against unification a step further by offering a justification for maintaining the division between common law estoppels and equitable estoppels. They should remain divided because each category serves discrete norms. The norms informing common law estoppels also define the limits to the operation and effect of common law estoppels. As is shown below, detriment is irrelevant as a control mechanism for common law estoppels and it is not necessary to understand these estoppels as being bounded by the line between facts and promises.

This article is concerned with vertical coherence in the sense of the relationship between a doctrine of law and its underlying normative aim. Coherence might also raise the question whether the individual estoppels existing within the categories of common law estoppels and equitable estoppels can and should be unified.[12] Likewise, horizontal coherence in terms of the alignment between estoppel doctrines and other adjacent doctrines, like contract,[13] might be considered. Ultimately, these are questions for another day. The ability to effect reform on the basis of coherence in both of these senses cannot be determined until the norms informing common law estoppels and equitable estoppels have been identified and understood. The aim of this article is to offer an account of those norms with a view to providing an explanation of how vertical coherence is best served in this instance by the separation of these two categories of estoppels, rather than unification.

II The Division between Common Law Estoppels and Equitable Estoppels

In order to understand how separate categories of estoppels pursue different normative goals, it is first necessary to understand what common law estoppels and equitable estoppels do, and how they differ. The fundamental difference between them is that each relates to discrete inquiries that occur within the process of litigation. A court must first ascertain what state of affairs exists between the parties to determine the second inquiry, which is as to the substantive rights and obligations that arise in response to the state of affairs. Common law estoppels speak to the first question of what is the state of affairs between the parties, and operate as rules of evidence and procedure that help to define the state of affairs to be accepted by the court. Equitable estoppels speak to the second question, of whether the rights and obligations as claimed or denied, exist and why. Equitable estoppels are substantive principles of law because they are relevant to declaring an immediate right or claim between the parties to litigation.[14]

A Common Law Estoppels

Common law estoppels[15] can be raised in a case involving equitable rights or common law rights.[16] These estoppels speak to the preliminary inquiry of what state of affairs exists between the parties and according to which their rights and obligations are decided. This inquiry is one that can be determined in various ways. The scope of this inquiry will be defined by the pleadings.[17] In their pleadings, each party will provide its own account of the state of affairs as relevant to their cause of action or defence.[18] Where the parties plead the existence of the same state of affairs, or one party accepts the pleadings of the other party as to a particular matter, then that common or agreed state of affairs will be accepted by the court as in existence between the parties. But where the parties have conflicting accounts, it becomes necessary for a determination to be made as to the state of affairs that the court should accept. This could be a function of what evidence a party can adduce to prove the factual existence (or non-existence) of a certain state of affairs. Alternatively, the question of what state of affairs should be accepted by a court could be answered by a common law estoppel.

A common law estoppel can be understood as a procedural right because it creates a right in favour of B to control the process of litigation in a particular way; namely to preserve a particular state of affairs accepted by the court as in existence between A and B. The state of affairs to be preserved by a common law estoppel might be as to the existence (or non-existence) of facts or rights.[19] Common law estoppels are not, however, a source of substantive rights and obligations like contract, tort or equitable estoppels. Common law estoppels are only concerned with the terms upon which those rights and obligations are to be decided. Brennan J has explained that ‘[t]he effect of an estoppel in pais is not to create a right in one party against the other; it is to establish the state of affairs by reference to which the legal relationship between them is ascertained’.[20]

In other words, the parties to a common law estoppel are not bound by the estoppel, but are bound to the state of affairs maintained by the estoppel. An archetype is Grundt v Great Boulder Pty Gold Mines Ltd,[21] in which a group of gold miners, represented by B, had been given a licence to mine a particular area for gold. The miners had, in fact, mined outside the area covered by the licence agreement. B sought a declaration that B had been mining within the area covered by the licence agreement. The owner of the mine, A, sought compensation for trespass from B. B raised an estoppel by convention on the basis that A and B had assumed as the conventional basis for their relationship that a particular state of affairs existed, specifically that the area being mined was within the area covered by the licence agreement. An estoppel by convention is ‘a form of estoppel founded ... on the conduct of relations between the parties on the basis of an agreed or assumed state of facts, which both will be estopped from denying’.[22]

Ultimately, an estoppel by convention did not arise in Grundt, because there was no conventional understanding between the parties that B was mining within the agreed area.[23] However, it was acknowledged that if estoppel by convention had been made out, the estoppel would have operated to preserve the state of affairs assumed by the parties as the conventional basis of their relationship, and according to which the parties’ substantive rights and obligations would be determined.[24] Chief Justice Latham indicated that estoppel ‘operates as a rule of evidence to prevent [A] from proving and relying upon the statement of fact which was the necessary foundation of any claim for trespass’.[25] His Honour explained that an estoppel ‘precludes a person from proving and relying on a particular fact’.[26] Estoppel was distinguished from other doctrines that are relevant to the next stage of inquiry in litigation, being the determination of the substantive rights and obligations in existence between the parties, such as waiver, ‘which involves the abandonment of a right’.[27] Justice Dixon observed that had an estoppel by convention been raised, then ‘[b]y adopting such a common assumption as the basis of their working relations, the parties would each be precluded from denying it for any purposes arising out of the tribute agreement’.[28]

If an estoppel by convention had arisen in Grundt, it would have maintained a particular state of affairs, specifically that B had permission to mine the relevant area of mine. According to that state of affairs, A’s claim would have failed because the requisite facts could not be established and B would have had a defence given A’s consent (a fact proved by the estoppel). The estoppel would not have operated as conferring a right on B to restrain A from relying upon A’s rights under trespass or otherwise to extinguish A’s rights against B, it simply changed the state of affairs according to which A’s claim would be decided. In this way, common law estoppels can have an indirect, but no less serious, effect on the existence of the rights and obligations arising between the parties.

The various common law estoppels operate in different ways to preserve a particular state of affairs. For example, estoppels by record, like cause of action estoppel or issue estoppel, maintain a particular state of affairs, such as the finality of preceding litigation by controlling the conduct of proceeding litigation.[29] Estoppels by record ensure the finality of litigation by preventing a particular cause of action, or issue of fact or law from being raised.

Other estoppels, like estoppel by deed and the estoppels derived from estoppel in pais, maintain a particular state of affairs previously adopted by the parties. Adoption refers to the parties’ acceptance of the existence of a particular state of affairs for the purposes of their legal relationship. The elements of these estoppels test for adoption and ensure that an off-the-cuff comment by A, or B’s unreasonable expectation and reliance do not raise an estoppel. For example, to raise an estoppel by representation, subjective and objective inquiries are employed to test whether A and B have accepted a particular state of affairs. Party A must have intended her representation (that a particular state of affairs exists) be acted upon by B, which is determined by an objective inquiry according to the terms of A’s representation.[30] B must subjectively accept the existence of the state of affairs as represented by A, which is demonstrated by the elements requiring proof of B’s actual expectation that has motivated some externalised action on B’s part, as shown by detrimental reliance. However, B’s adoption of the state of affairs must also conform to objective standards as B’s expectation and detrimental reliance must be reasonable.[31] There are various ways in which the parties might adopt a state of affairs and there are different estoppels that respond to these modes of adoption. For example, an estoppel by deed will maintain the state of affairs as set out in a deed, where entry into the deed itself demonstrates adoption.[32] An estoppel by convention will maintain the state of affairs as accepted by the parties as the conventional basis of their relationship, and the elements this estoppel require that the parties have accepted this state of affairs as such.

A state of affairs can be maintained by one of these estoppels through its operation as a rule of evidence. That rule prevents the admission of evidence to prove facts that would contradict the state of affairs sought to be maintained by the estoppel.[33] These estoppels are not only rules of evidence in that they restrict the admission of evidence,[34] they can also supersede the need for B to adduce evidence to prove the existence of a state of affairs. The estoppel operates as an admission on the part of A (and B) that a particular state of affairs exists.[35] Hence, common law estoppels can maintain a state of affairs, either by controlling the admission of evidence by A, or by providing proof of the existence of the particular state of affairs to be maintained by the estoppel.

Finally, it should be acknowledged that the characterisation of those common law estoppels derived from estoppel in pais as rules of evidence and procedure, as opposed to substantive estoppel doctrines, is not uncontroversial. For example, it has been argued that estoppel by representation and estoppel by convention are no longer rules of evidence, but are substantive estoppel doctrines like equitable estoppels.[36] To a large extent, the arguments made in favour of characterisation of estoppels in pais as substantive estoppels is based upon the view that these estoppels should be so characterised on the basis of an identified normative rationale.[37] That approach has been considered elsewhere.[38] This article is concerned with the question whether estoppels in pais should be merged with their equitable counterparts. For the reasons discussed below, the normative rationale informing estoppels in pais dictates their separate existence and operation as rules of evidence and procedure rather than as substantive estoppels, so that much of the force in favour of the substantive characterisation of estoppels in pais is disengaged.

B Equitable Estoppels

Equitable estoppels[39] are not concerned with the question of what is the state of affairs in existence between the parties. Equitable estoppels answer a different question that arises in litigation: what are the parties’ rights and obligations? Unlike common law estoppels, equitable estoppels are themselves a source of rights and obligations that arise upon satisfaction of the necessary elements, albeit subject to equitable discretion. Take proprietary estoppel as an example. A proprietary estoppel can be raised where A has made a representation or assurance to B which causes B to believe he or she has or will acquire an interest in property, which has been relied upon by B such that B will suffer detriment should A be allowed to depart the assumption.[40] For example, in Thorner v Major,[41] various promises were made by A to B, to the effect that B would inherit A’s farm. In reliance upon A’s promises, B did substantial work on A’s farm for 30 years without pay. A died without leaving a will. B successfully claimed a beneficial interest in the farm against A’s estate on the basis of a proprietary estoppel. Proprietary estoppel created an equity in B’s favour that bound A’s estate.[42] Similarly, in cases like Gillett v Holt,[43] Giumelli v Giumelli[44] and Sidhu v Van Dyke,[45] a proprietary estoppel arose in response to the real state of affairs existing between the parties and created in B’s favour a positive right to equitable relief against A.

Promissory estoppel also determines the rights and obligations between the parties in response to the actual state of affairs existing between them. The estoppel responds where A has made a promise or assurance to B upon which B reasonably relied in forming an expectation, and which induced B to change her position such that B will suffer detriment should A depart A’s promise.[46] A promissory estoppel confers upon B an enforceable right, for example, to seek an injunction that restrains the enforcement by A of her legal right.[47]

Once an equitable estoppel is made out, a right to equitable relief that binds A arises in favour of B.[48] A court will determine the extent of the equity raised by the equitable estoppel, which depends upon what is considered sufficient to remedy A’s unconscionable conduct.[49] The court then has a high degree of flexibility in exercising its discretion to determine the type of relief necessary to satisfy the equity, which takes account of a broad range of considerations beyond those relevant to A’s unconscionable conduct, and includes, for example, the interests of third parties.[50] The operation of an equitable estoppel is very different to a common law estoppel. An equitable estoppel creates rights and obligations between the parties, whereas a common law estoppel maintains a particular state of affairs according to which the parties’ rights and obligations are determined.

III The Normative Foundations Informing Common Law Estoppels and Equitable Estoppels

Judges and academics propose different schemes according to which estoppels may be ordered and catalogued. The nuances of that debate lie beyond this discussion, save to notice that irrespective which scheme or proposal for reform has been suggested, all rest on the assumption that the normative underpinnings of a doctrine are relevant and should have some role in understanding and shaping an estoppel doctrine.[51] To this end, the prevention of detriment has been identified as the normative rationale of both common law estoppels and equitable estoppels.[52] Contrary to the prevailing view, this analysis advances the position that common law estoppels and equitable estoppels do not share a common purpose of the prevention of detriment. Common law estoppels and equitable estoppels are each informed by discrete normative rationales so that coherence is best served by a separation of these categories of estoppels, rather than unification. Any abandonment of the divide between certain common law estoppels and equitable estoppels, and reformulation of these common law estoppels to achieve coherence, would come at a high price. That price being a lack of coherence between common law estoppels and their true normative foundations.

There are three primary norms that inform various common law estoppels. The first informs estoppels by record, such as cause of action estoppel and issue estoppel, and is the public interest in ensuring the finality of litigation and the private interests of the parties that a person should not be ‘vexed twice for the same cause’.[53] A second norm has also been recognised as informing cause of action and issue estoppel[54] according to the maxim, res judicata pro veritate accipitur, which refers to the need for the decisions of the courts, unless set aside or quashed, to be accepted as incontrovertibly correct.

The third norm relates to other common law estoppels, such as estoppel by deed, and estoppels in pais, which is that the parties should be held to a particular state of affairs in litigation to preserve party autonomy. This norm has previously been identified as informing estoppel by representation[55] and this analysis explains the relevance of this norm to other common law estoppels. Where the parties conduct their relationship on the basis that a particular state of affairs exists, then the legal consequences of that relationship ought to be determined according to the same state of affairs as previously adopted by the parties, irrespective the truth.[56] Lord Blackburn explained the rationale in the following way:

When a person makes to another the representation ... [that] such and such things do exist, and you may act upon the basis that they do exist, it seems to me it is of the very essence of justice that, between these two parties, their rights shall be regulated, not by the real state of facts, but by that conventional state of facts ...[57]

Similarly, in Lavarello, the Board explained the rationale as follows: ‘The meaning of estoppel is this — that the parties agreed, for the purpose of a particular transaction, to state certain facts as true; and that, so far as regards that transaction, there shall be no question about them.’[58]

The reference to the ‘agreed’ state of affairs does not confine the sphere of concern for common law estoppels to situations where the parties contractually agree what state of affairs exists between them. Rather, these estoppels operate where the parties have adopted a particular state of affairs for the purposes of their relationship, irrespective the means by which that state of affairs is adopted. In addition to contract, the parties might adopt a particular state of affairs through a deed, or by way of a representation made by A upon which B relies. As discussed above, the different common law estoppels respond to the different ways in which parties adopt a particular state of affairs. But the aim and effect of each is the same: to maintain that state of affairs when the legal consequences of the parties’ relationship come to be determined in litigation.

Party autonomy has been identified before as a reason why the parties ought to be held to a particular state of affairs. In Lavarello, it was explained that holding parties to the state of affairs as previously adopted by them ‘accords with the principle of party autonomy which underlies the common law of contract’.[59] The reference to contract refers only to the fact that party autonomy is a norm underpinning each of the doctrines of contract and estoppel, but these doctrines otherwise serve distinct purposes. Contract determines what are the parties’ rights and obligations, whereas common law estoppels determine what state of affairs exists between the parties and according to which their rights and obligations would then be determined. Party autonomy can explain why contractual rights and obligations are recognised and enforced. In relation to common law estoppels, party autonomy explains why a particular state of affairs should be maintained for the purposes of litigation. The one norm of party autonomy informs each doctrine.

The principle of party autonomy as it applies to common law estoppels is that the parties are free to choose the basis upon which they conduct their legal relationship, which might be according to a certain state of affairs, even if it is not the true state of affairs. Not only can parties choose the basis upon which they conduct their relationship, but where such a choice has been made, then in some situations the parties should be bound by their choice. The situations in which the parties should be bound are where the adopted state of affairs has formed a reason for (in)action for B in the decisions he or she makes regarding her relationship with A. As discussed above, the elements of the different common law estoppels, such as reliance and detriment, or entry into a deed or contract, test that a particular state of affairs has been adopted by the parties for their legal relationship and has formed a reason for (in)action for B.

The parties should be bound to that state of affairs in litigation because to allow one party to the relationship, A, to depart from the adopted state of affairs would infringe the decision-making autonomy of B. The reason for the concern for B’s decision-making autonomy in the context of litigation between A and B, is that litigation determines conclusively the rights and obligations between the parties arising from their relationship.[60] The seriousness of the consequences of litigation dictates that the court ought not overlook B’s reasons for (in)action where those reasons have influenced her relationship with A, the legal consequences of which are now the subject of the court’s attention. A common law estoppel ensures that B’s reason for (in)action is maintained by preserving the state of affairs adopted by the parties for their relationship.

Contrary to the argument made here is the view that the goal of those common law estoppels derived from estoppel in pais, and equitable estoppels is the prevention of detriment.[61] Following from this, it is the existence of a common purpose of the prevention of detriment that then provides an underlying unity to support the emergence of one overarching doctrine of estoppel, rather than a series of independent rules. On the basis of coherence, it has been suggested that some categories of estoppels should be merged so that the same ends can be achieved by the same means.[62] For the reasons discussed next, the prevention of detriment is not the driving normative force behind common law estoppels, or equitable estoppels and, consequently, does not provide a sound basis upon which to suggest reforms in the name of coherence.

Support for the view that the norm informing estoppels in pais and equitable estoppels is the prevention of detriment, is said[63] to be found in the judgement of Dixon J in Grundt. In Grundt, His Honour stated:

[t]he principle upon which estoppel in pais is founded is that the law should not permit an unjust departure by a party from an assumption of fact which he has caused another party to adopt or accept for the purpose of their legal relations. ... [T]he rules governing estoppel ... work out the more precise grounds upon which the law holds a party disentitled to depart from an assumption in the assertion of rights against another ... [T]he basal purpose of the doctrine ... is to avoid or prevent a detriment to the party asserting the estoppel by compelling the opposite party to adhere to the assumption upon which the former acted or abstained from acting.[64]

The submission of this article is that like estoppel by representation, other estoppels in pais — such as estoppel by convention and estoppel by deed — are concerned with maintaining a particular state of affairs in litigation, not the prevention of detriment. As explained above, there are important reasons why a state of affairs must be maintained and the prevention of detriment is not one. True, Dixon J does state that estoppel in pais is concerned to ‘prevent a detriment to the party asserting the estoppel’.[65] However, Dixon J’s statements cannot be reduced to mean that the purpose of estoppel in pais is the prevention of detriment. Such an abstraction is not consistent with the broader context of Dixon J’s statement in Grundt, from which the description of this purpose is said to have emanated. Considering that the interpretation of a judgment is not the same process as statutory construction,[66] the reference by Dixon J to the ‘basal purpose of the doctrine’[67] must be read in the context of the other statements made in Grundt that, in fact, support identification of the purpose of common law estoppels as the maintenance of a particular state of affairs. Justice Dixon states that estoppel in pais is concerned with when ‘[t]he law holds a party disentitled to depart from an assumption in the assertion of rights against another’.[68]

Justice Dixon further explains that the ‘justice of an estoppel’ is not only concerned with when ‘a departure from the assumption would turn the action or inaction into a detrimental change of position’.[69] An estoppel in pais is concerned with when a state of affairs has been ‘adopt[ed] or accept[ed] or for the purpose of [the parties’] legal relations’ and ‘accepted as the foundation of the rights and duties’ between the parties.[70] Estoppels avoid injustice by ensuring that the determination of the parties’ rights and obligations is made according to the same state of affairs adopted by them as the foundation of their relationship. It should be remembered that had an estoppel by convention arose in Grundt, the estoppel would have operated to preserve the state of affairs assumed by the parties as the conventional basis of their relationship.[71] There was no suggestion that the effect of the estoppel would have been, or should have been, confined to the level of detriment necessary to raise it.

Detriment is not the reason why the parties should be held to a particular state of affairs. However, detriment does, sometimes, have a role to play in demonstrating that a state of affairs has been adopted by the parties. This is why detriment is one of the elements necessary to make out some common law estoppels. For example, estoppel by representation requires B to demonstrate that some detriment would be suffered by B should A be allowed to depart the assumed state of affairs in litigation.[72] This detriment needs to be substantial, but need not be financially quantifiable.[73] The normative significance of detriment is that it, along with other elements such as reasonable reliance, demonstrates that a particular state of affairs has been accepted by B and formed a reason for (in)action for B. Thus, detriment can be one of the preconditions for when the law is concerned with B’s decision-making autonomy. Detriment is not however, the reason why the law is concerned with B’s decision-making autonomy, nor the reason why a common law estoppel arises.

The limited role of detriment within common law estoppels, can be observed by turning to another common law estoppel for which detriment is not a requirement: estoppel by deed.[74] Detriment is not a requirement because it has no role to play. Detriment has no work to do in demonstrating the adoption of a state of affairs, because this is already demonstrated by the parties’ execution of the deed. Execution of a deed is one of the most solemn acts that can be undertaken by a party,[75] so that the adoption of a state of affairs is inherent in and already demonstrated by the event giving rise to the estoppel itself.

Turning to equitable estoppels — even here, the prevention of detriment is not the sole purpose or rationale informing equitable estoppels. True, the purpose of equitable estoppels has been described as the prevention of detriment[76] and support for this view is also said to be derived from Dixon J’s statement in Grundt, extracted above.[77] But ultimately equitable estoppels, like other equitable doctrines, are concerned with remedying A’s unconscionable conduct.[78] In the context of equitable estoppels, unconscionability is a function of B’s unfulfilled expectation, B’s detriment, and the extent to which A’s conduct caused B’s expectation and detriment.[79] Detriment is, thus, not the only variable and is not the reason why an equitable estoppel arises.[80] Equitable estoppels are also concerned with B’s expectation and the extent to which that expectation has been induced by A’s conduct.[81]

As equitable estoppels are not solely concerned with the prevention of detriment, it should not be surprising that the relief for an equitable estoppel is not confined to what is necessary to prevent B’s detriment and the relief may be designed to give effect to B’s expectation.[82] In Ashton v Pratt, Bathurst CJ stated:

[w]hat now appears clear is that there is no need to mould any remedy in the case of equitable estoppel to reflect the minimum relief necessary to remove the detriment. Prima facie the courts should enforce a reasonable expectation which [A] created or encouraged.[83]

Thus, the overriding concern is with the prevention of unconscionability, which is a function of more than B’s unfulfilled expectation or B’s detriment. Vindication of B’s expectations is not always the endpoint. Party A will only be held responsible for B’s expectation to the extent it was induced by A’s conduct. That is, there must also be some proportionality between B’s detriment, the extent of the equity raised, and the relief ultimately awarded.[84] Detriment has a role to play in explaining when and why an equitable estoppel arises, but the prevention of detriment is not the sole or fundamental purpose of equitable estoppels.

Even if these arguments in relation to detriment are not accepted, then it is submitted that the presence of a common goal, such as the prevention of detriment, does not necessarily support unification of common law estoppels and equitable estoppels. It is possible for doctrines to serve the same normative rationale, but in different, yet equally valid, ways. Even if detriment does have some role in each of common law estoppels and equitable estoppels, these estoppel doctrines have different spheres of operation that tend against unification. Common law estoppels are concerned with the question of what state of affairs should be accepted as in existence between the parties to litigation, whereas equitable estoppels speak to a different question in litigation; namely, to what are the rights and obligations existing between the parties.

Along similar lines, party autonomy does not provide a conceptual plinth for unification. It might be argued that equitable estoppels are concerned with party autonomy, like some common law estoppels: it is unconscionable for A to depart her promise to B due to the fact that A’s conduct has provided a reason for (in)action for B, and B’s decision-making autonomy would be infringed should A be allowed to depart her promise. So the argument might go that party autonomy provides a common basis upon which some common law estoppels, could be merged with equitable estoppels. Again, a common normative aim does not provide a basis for unification.

Coherence between doctrines that serve fundamentally distinct purposes is not desirable simply because the same underlying norm can be identified as informing each doctrine. To unify on the basis of a common norm of party autonomy would be like unifying the law of contract with that of deceit or misrepresentation on the ground that each could be understood as concerned with party autonomy. Ultimately, the price for some degree of superficial coherence on the basis of similar labels, will be a loss of coherence in a much more meaningful sense.

Reconfiguration of common law estoppels as substantive estoppel doctrines would destroy any coherence between the doctrine and its normative rationale: of controlling the state of affairs between the parties in the course of litigation to protect party autonomy. An equitable estoppel, and any common law estoppel reconfigured as such, cannot remain true to this normative commitment. This is because not all equitable estoppels create positive rights in B’s favour to require the maintenance of the assumed state of affairs.[85] Even when a positive right is created by an equitable estoppel, B may only be entitled to prevention of her detriment, not the preservation of the assumed state of affairs. An equitable estoppel cannot do the work of a common law estoppel.

Another suggested basis for unification does not focus upon a common norm or rationale, but rather looks to the existence of common themes or elements that otherwise provide some basis upon which connections between some common law estoppels and equitable estoppels can be drawn.[86] To this end, it has been observed that estoppel by representation, estoppel by convention, promissory estoppel and proprietary estoppel have in common the elements of reasonable reliance and detriment.[87] It is then argued that these common elements point towards the desirability of recognising a unified doctrine of reliance based estoppel.

It is submitted that the existence of elements that might be similar in name and even content, such as reasonable reliance and detriment, do not provide a basis upon which some common law estoppels and equitable estoppels can be unified. This is because reasonable reliance and detriment have different roles to play within equitable estoppels and common law estoppels. Within common law estoppels, reasonable reliance and detriment demonstrate that a state of affairs has been adopted by the parties, but are not the reason why a particular state of affairs should be maintained. Within equitable estoppels, reasonable reliance and detriment are part of the state of affairs to which these estoppels respond and they have a role to play in defining the measure of relief to an equitable estoppel. Given the different roles these elements play, they do not provide any conceptual connection between common law estoppels and equitable estoppels.

Commentary has readily assumed that there is no normative justification why estoppels in pais, such as estoppel by representation and estoppel by convention, operate as rules of evidence and procedure.[88] But for the reasons discussed above, these estoppels do not operate as rules of evidence and procedure simply due to quirks of historical development. There is a normative explanation why these common law estoppels do, and should continue to, hold the parties to a particular state of affairs for the purposes of litigation between them. The underlying norm of party autonomy justifies the operation of estoppels in pais, and ultimately justifies the preservation of the divide between those estoppels and equitable estoppels. In order to ensure coherence between these separate categories of estoppel doctrines and their underlying rationales, it is necessary that the divide between remain.

IV (Re)defining the Limits to Common Law Estoppels

One of the primary consequences of acceptance of the fact that common law estoppels and equitable estoppels serve different normative rationales is that the control mechanisms so far relied upon to limit the scope and effect of estoppels in pais should be abandoned. But this does not mean that estoppels in pais are unlimited. There are other important limitations to the scope and effect of these estoppels that ensure coherence between the estoppel doctrine and its underlying normative rationale.

The limits to estoppels in pais are of heightened significance given the potential for such estoppels to have an all-or-nothing effect.[89] Recall, an estoppel in pais operates to preserve a particular state of affairs by precluding the admission of evidence or constituting positive proof of the existence of a certain state of affairs. There is no halfway position; the evidence is either admissible or it is not, and the existence of a particular state of affairs is either accepted or it is not. Even though estoppels in pais are not a source of substantive rights and obligations, they nonetheless may have a determinative impact on the outcome of a case. Estoppels in pais can change the outcome of a case by changing the state of affairs accepted by a court as in existence between the parties. Further, the effect of an estoppel in pais is not calibrated according to the level of detriment necessary for B to make out the estoppel in the first place. In Kelly v Fraser, Lord Sumption explained that ‘the ordinary rule is that detriment is not the measure of [B]’s relief’.[90] Depending on the circumstances of the case, B could be left better off by the estoppel.[91] The allornothing effect of an estoppel in pais is in stark contrast to an equitable estoppel, where there is a high degree of flexibility available to the court when fashioning relief to meet the equity raised by an equitable estoppel.[92]

In the search for some control mechanism or limit to the all-or-nothing effect of estoppels in pais, it has been suggested that detriment should play a role in defining the limits to these estoppels.[93] There is the concern that estoppels in pais should not be ‘confined to producing an all-or-nothing consequence where that consequence would undermine the rationale for its operation’.[94] But these concerns and suggestions arise on the assumption that the underlying purpose of such estoppels is the prevention of detriment. The all-or-nothing effect of estoppel in pais is thought to create a disconnect between the individual estoppel doctrines and their underlying purpose on the basis that, in some cases, an estoppel in pais may go beyond preventing B’s detriment and leave B better off. Accordingly, there have been proposals for estoppels in pais to be reconfigured as a substantive estoppel doctrine like an equitable estoppel and would be limited to the level of detriment required to raise the estoppel.[95] In addition, English courts have been prepared to apply an exception to the all-or-nothing operation of estoppel by representation so that its operation is limited to the amount of B’s detriment.[96]

If the arguments made in this article as to the true normative foundations of estoppels in pais are accepted, then a key implication is that detriment is rendered irrelevant as a control mechanism or limit. The prevention of detriment is not the common purpose or normative rationale of estoppels in pais. Limiting the operation of these estoppels to the level of detriment would result in a rupture between the estoppel and its true normative foundations, being the preservation of a state of affairs in litigation for the sake of party autonomy. True, this may well mean that, in some circumstances, the effect of an estoppel will go beyond the level of detriment required to make out the estoppel. For example, B might be left better off by raising an estoppel than he or she would have been had A not made her representation. However, this result is justified according to the applicable normative rationale: that the parties should be held to the state of affairs in litigation where that state of affairs was previously adopted by them for the purposes of their relationship. If A and B have adopted a particular state of affairs for the purposes of their relationship, then the fact that an estoppel in pais, such as estoppel by conduct or estoppel by representation, might operate beyond the level of B’s detriment is neither here nor there.

The irrelevance of detriment as a control mechanism can be seen from another angle. Just as detriment does not set a maximum limit to the effect of estoppel in pais, nor does it set a minimum floor. An estoppel in pais does not impose an obligation on A to make up for B’s detriment. So, in some circumstances, it is possible that even where A is held to the represented state of affairs in litigation, B’s detriment may still be left unaddressed. The prevention of detriment is not the purpose of an estoppel in pais and so its prevention or otherwise does not determine the effect of the estoppel. Detriment is relevant only to showing that B has adopted the state of affairs in making decisions about her relationship with A.

Albeit abandonment of detriment as a control mechanism does not mean that estoppels in pais are unlimited. There are three significant limits to the operation and effect of estoppels in pais. First, the parties will only be bound to a particular state of affairs by the estoppel where they have actually adopted that state of affairs for the purposes of their relationship. For example, A will only be held to a state of affairs by an estoppel by representation where A has made an unequivocal and unambiguous representation[97] and where A intended the statement would be acted upon by B (objectively determined).[98] B must have also adopted the state of affairs in some way, for example, by changing her position. There are further controls: B’s change of position must be such that B would suffer material detriment if A is allowed to depart her representation[99] and B’s change must also be reasonable in light of A’s representation.[100] Case law demonstrates that these elements are relatively high hurdles to make out in social and commercial dealings.[101] It is not the case that any or all representations made by A, or other conduct by A, will result in B having an estoppel in her favour. As Lord Cranworth LC explained in Jorden v Money, ‘[i]t will not do if he merely said something ... and then that some stranger, having heard and acted upon it, should afterwards come to him to make it good.’[102] There are limitations in-built into the elemental requirements that ensure coherence between the operation of the estoppel doctrine and its underlying rationale: it is only when A and B have actually adopted a certain state of affairs for their relations, and where the existence of that state of affairs has formed a reason for action for B, that an estoppel in pais can be raised.

Second, the area in which protection is given to B’s decision-making autonomy by estoppels in pais is very limited. An estoppel in pais is not concerned with giving B a right to enforce an obligation on A to make good the assumed state of affairs. Nor does an estoppel in pais create a negative right in B’s favour to restrain the enforcement of A’s rights. It is only in relation to the question as to what state of affairs should be accepted as in existence between the parties that an estoppel in pais is concerned with B’s decision-making autonomy. All these estoppels can do is to ensure that a particular state of affairs is accepted by a court for the purposes of the court then determining the parties’ substantive rights and obligations. Protection is given to B’s decision-making autonomy only in the context of controlling the process of litigation between A and B.

Third, party autonomy defines when and why an estoppel in pais arises and also provides further limits to these estoppels. For example, B will not be able to raise an estoppel in pais to hold A to a particular state of affairs where to do so would infringe A’s decision-making autonomy. For example, an estoppel in pais cannot be raised if A was induced by fraud or undue influence to enter into a deed or contract, or to make a representation.[103] Albeit the protection granted to A’s autonomy is limited. For example, if A mistakenly makes a representation or otherwise adopts a particular state of affairs, A might still be held to that state of affairs, providing the other elements of the estoppel are made out.[104] The limits to the concern for A’s decision-making autonomy are paralleled elsewhere. For example, the mistake of one party will not vitiate a contract, in the absence of other factors.[105] Party A might enter into a contract under some mistake and yet be bound by contractual obligations that confer substantive rights in favour of B against A. Illegality is another example of the limits placed upon party autonomy in the context of estoppels in pais.[106]

An estoppel in pais will not hold the parties to a state of affairs where that state of affairs contemplates an illegal outcome, such as the assumption of powers which are ultra vires,[107] or the subversion of a statute.[108] This is so irrespective whether the parties chose to adopt that particular state of affairs for the purposes of their legal relationship. The role of illegality as a limit to party autonomy is also reflected elsewhere. For example, a contract for an illegal purpose will not be enforced.[109]

The final point is that the dividing line between representations of facts and promises has a limited, if any, role to play as a limitation to an estoppel in pais and other common law estoppels. The distinction between a representation of fact or promise has been relied upon as one of the key dividers between common law estoppels and equitable estoppels.[110] It is said that a common law estoppel can be raised only where a representation of fact has been made where as an equitable estoppel can be raised where a promise or representation as to a future state of affairs has been made.[111] However, the distinction between representations of fact and promises is not actually a limitation to the operation of common law estoppels. This is because both a common law estoppel and an equitable estoppel can be raised regardless of whether a statement of fact or a promise has been made by A.

Previous statements[112] to the effect a common law estoppel cannot be raised where a promise has been made, really relate to the fact that a useful common law estoppel cannot be raised outside the situation where a statement as to an existing state of affairs has been made. An example will demonstrate. Party A promises B that A will accept a reduced rate of rent. Party A later sues to recover the higher rent. B could raise an equitable estoppel, to restrain A’s enforcement of A’s right to the higher rent for a period of time.[113] B could have also raised a common law estoppel like estoppel by representation, estoppel by conduct or estoppel by convention (depending on how the state of affairs is adopted by the parties), even though A’s statement is a promise. The common law estoppel would have maintained the state of affairs adopted by the parties for the purposes of their legal relationship. That state of affairs is that A has promised it would not enforce A’s right to the higher rate of rent. This common law estoppel will be of little utility to B in defending A’s claim because a common law estoppel does not operate to create any right in B’s favour to enforce A’s promise,[114] nor does it create a right in B’s favour to restrain the enforcement by A of her right to the higher rate of rent. A common law estoppel simply prevents A from later denying the fact the promise was made and the fact that A has made a promise does not help B’s case, unless B can also make out the elements required for a contract, or a promissory estoppel. In this example, the distinction between a representation of fact and a promise does not determine whether a common law estoppel or an equitable estoppel can be raised. Although, the distinction does drive whether a common law estoppel will be of any strategic value to B. It is important to observe that the reason why a common law estoppel is of less utility where a promise is made, lies in the application of substantive principles of law, for example the requirement for consideration for a promise to be enforceable. Common law estoppels do not, according to their own terms, distinguish between facts or promises.

The distinction between a representation of fact and a promise has also been a motivating factor to abandon the division between certain common law estoppels and equitable estoppels.[115] This criticism is misplaced because, for the reasons just discussed, the distinction between a fact or promise does not drive the application of different estoppels nor operates as a limit to common law estoppels or equitable estoppels and thus is not a basis for reform or unification.

V Conclusion

There is mounting pressure for certain common law estoppels to be recast and realigned with equitable estoppels for the sake of coherence. This article has urged caution before any decisive step is taken towards abandoning the division between some common law estoppels and equitable estoppels. Such a step would come at the price of a more meaningful type of coherence: that between a doctrine of law and its underlying rationale. Coherence is best achieved by maintaining the separation of categories of estoppels according to their true underlying norms. Common law estoppels are concerned with preserving a particular state of affairs between parties to litigation in order to serve the public and private interests in finality of litigation, or to preserve the parties’ decision-making autonomy, depending on which discrete common law estoppel is engaged. Equitable estoppels, on the other hand, are concerned with assigning responsibility to A for B’s unfulfilled expectation and detriment to remedy A’s unconscionable conduct. Equitable estoppels and common law estoppels are not informed by a common purpose or common rationale that motivates alignment for the sake of coherence. Maintaining a division between these categories of estoppels will not result in arbitrary or unjust results. Nor will the operation and effect of common law estoppels be left unbridled. There are already significant limits that confine common law estoppels in their operation and effect. These limits necessitate against the introduction of further limits on the basis of a misperceived need for coherence with the non-existent purpose of prevention of detriment.


[∗] LLB/BA (UNSW), BCL (Oxon), Senior Lecturer, UNSW Law. I am very grateful to Elise Bant, Simone Degeling, Matthew Harding, Ben McFarlane, Andrew Robertson, Philip Santucci, Peter Turner, Greg Weeks and Sarah Worthington for their assistance in earlier drafts of this article and for the helpful comments of the anonymous referees. All errors remain my own.

[1] How coherence is achieved is a different matter that may be the subject of debate, but lies beyond the scope of this article, see, eg, Sullivan v Moody (2001) 207 CLR 562, 576 [42], 579–80 [50], 581 [55] (Gleeson CJ, Gaudron, McHugh, Hayne and Callinan JJ); Agricultural & Rural Finance Pty Ltd v Gardiner [2008] HCA 57; (2008) 238 CLR 570, 602 [100] (Gummow, Hayne and Kiefel JJ); Equuscorp Pty Ltd v Haxton (2012) 246 CLR 498, 513 [23], 523 [45] (French CJ, Crennan and Kiefel JJ); McFarlane v Tayside Health Board [1999] UKHL 50; [2000] 2 AC 59, 83 (Lord Steyn), 108 (Lord Millett); Ernest J Weinrib,

The Idea of Private Law (Harvard University Press, 1995) 8–14, 32–6; Neil MacCormick, Legal Reasoning and Legal Theory (Clarendon Press, 1978) 152; Barbara Baum Levenbook, ‘The Role of Coherence in Legal Reasoning’ (1984) 3(3) Law and Philosophy 355, 360; Andrew Burrows, ‘The Relationship Between Common Law and Statute in the Law of Obligations’ (2012) 128 (April) Law Quarterly Review 232, 233; Elise Bant, ‘Statute and Common Law: Interaction and Influence in Light of the Principle of Coherence’ [2015] UNSWLawJl 13; (2015) 38(1) University of New South Wales Law Journal 367,

367–9; Elise Bant and Michael Bryan, ‘Fact, Future and Fiction: Risk and Reasonable Reliance in Estoppel’ (2015) 35(3) Oxford Journal of Legal Studies 427, 430, 452.

[2] For an account of the different forms of coherence and its role in private law, see, eg, Andrew Robertson, ‘Constraints on Policy-Based Reasoning in Private Law’ in Andrew Robertson and Tang Hang Wu (eds), The Goals of Private Law (Hart Publishing, 2009) 261; Keith Mason, ‘Strong Coherence, Strong Fusion, Continuing Categorical Confusion: The High Court’s Latest Contributions to the Law of Restitution’ (2015) 39(3) Australian Bar Review 284, 296.

[3] See also Australian Financial Services & Leasing Pty Ltd v Hills Industries Ltd [2014] HCA 14; (2014) 253 CLR 560, 623–4 [153] (Gageler J) (‘Australian Financial Services & Leasing’). Outside estoppels, see Cavendish Square Holding BV v Makdessi [2015] UKSC 67; [2016] AC 1172, 1199 [22] (Lord Neuberger and Lord Sumption, with whom Lord Carnwath agreed). Coherence has also been understood in terms of an alignment between different doctrines of law, such as equitable estoppel and contract: Crown Melbourne Ltd v Cosmopolitan Hotel (Vic) Pty Ltd [2016] HCA 26; (2016) 90 ALJR 770, 797–8 [143]–[149] (Keane J) (‘Crown Melbourne’).

[4] Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 623–4 [153] (Gageler J); National Westminster Bank plc v Somer International (UK) Ltd [2001] EWCA Civ 970; [2002] QB 1286, 1299 [29], 1302–3 [37]–[38] (Potter LJ), 1307 [54] (Clarke LJ) (‘National Westminster Bank’); Eugene Fung and Lusina Ho, ‘Change of Position and Estoppel’ (2001) 117 (January) Law Quarterly Review 14, 19; Piers Feltham, Daniel Hochberg and Tom Leech (eds), Spencer Bower: The Law Relating to Estoppel by Representation (Tottel Publishing, 4th ed, 2004) [I.8.5]; Bant and Bryan, above n 1, 430, 452.

[5] Legione v Hateley [1983] HCA 11; (1983) 152 CLR 406, 432 (Mason and Deane JJ) (‘Legione’); Waltons Stores (Interstate) Ltd v Maher (1988) 164 CLR 387, 398–399 (Mason CJ and Wilson J), 415 (Brennan J), 459 (Gaudron J) (‘Waltons Stores’); Central London Property Trust Ltd v High Trees House Ltd [1946] EWHC KB 1; [1947] 1 KB 130, 134 (Denning J) (‘High Trees’); Roebuck v Mungovin [1994] 2 AC 224, 235 (Lord Browne-Wilkinson); Feltham, Hochberg and Leech, above n 4, [II.4.1].

[6] See above n 4.

[7] Ibid.

[8] Jessica Hudson, ‘The True Purpose of Estoppel by Representation’ (2015) 32(3) Journal of Contract Law 275. These arguments have also been made in relation to estoppel by representation as it applies to claims for restitution of a mistaken payment: J Hudson, ‘Estoppel by Representation as a Defence to Unjust Enrichment — The Vine has not Withered Yet’ (2014) 22 Restitution Law Review 19.

[9] Having regard to the warning in Sidhu v Van Dyke [2014] HCA 19; (2014) 251 CLR 505, 511 [1] n 26 (French CJ, Kiefel, Bell and Keane JJ).

[10] See, eg, India v India Steamship Co Ltd; The Indian Grace [No 2] [1997] UKHL 40; [1998] AC 878, 914 (Lord Steyn); Justice Kenneth Handley, Estoppel by Conduct and Election (Sweet & Maxwell, 2nd ed, 2016) [1034]; Ben McFarlane, ‘The Limits to Estoppels’ (2013) 7(3) Journal of Equity 250;

Ben McFarlane, ‘Understanding Equitable Estoppel: From Metaphors to Better Laws’ (2013) 66(1) Current Legal Problems 267.

[11] See, eg, National Westminster Bank [2001] EWCA Civ 970; [2002] QB 1286, 1301 [35] (Potter LJ); Fung and Ho, above n 4, 18.

[12] See, eg, Crown Melbourne [2016] HCA 26; (2016) 90 ALJR 770, 781 [37]–[38] (French CJ, Kiefel and Bell JJ), 795 [133], 796–7 [139]–[146] (Keane J), 810–11 [215]–[217] (Nettle J); Ben McFarlane, ‘Equitable Estoppel as a Cause of Action: Neither One Thing nor Another’ in Simone Degeling, Justice James Edelman and James Goudkamp (eds), Contract in Commercial Law (Lawbook, 2016), 359.

[13] See, eg, Crown Melbourne [2016] HCA 26; (2016) 90 ALJR 770, 797–8 [143]–[149] (Keane J).

[14] London Joint Stock Bank Ltd v MacMillan [1918] AC 777, 818 (Viscount Haldane). Equitable estoppels have been referred to as ‘substantive estoppels’ in distinction to those estoppels that operate as rules of evidence and procedure: see, eg, Waltons Stores (1988) 164 CLR 387, 449 (Deane J); Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 623–4 [153] (Gageler J); Canada and Dominion Sugar Co Ltd v Canadian National (West Indies) Steamships Ltd [1947] AC 46, 56 (Lord Wright) (‘Canada and Dominion Sugar’); Justice Handley, above n 10, [1-009]; William Swadling, ‘Substance and Procedure in Equity’ (2016) 10(1) Journal of Equity 1, 18-21.

[15] The term common law estoppels encompasses those estoppels originating from the estoppels described by Sir Edward Coke in The First Part of the Institutes of the Laws of England, or a Commentary Upon Littleton (J & W T Clarke, 18th ed, 1832) vol 2, s 667 [352a]–[352b], being estoppel by record, estoppel by writing and estoppel in pais. Estoppel by record developed into cause of action estoppel, issue estoppel and the extentions of these estoppels based on abuse of process. Estoppel by writing is referred to as estoppel by deed. Estoppel in pais has since been developed into multiple sub-categories of estoppels, including estoppel by convention and estoppel by representation. This sub-category of estoppels, individually and collectively, continues to be referred to as estoppel in pais: Legione [1983] HCA 11; (1983) 152 CLR 406, 430 (Mason and Deane JJ); Waltons Stores (1988) 164 CLR 387, 413 (Brennan J); Caboche v Ramsay [1993] FCA 611; (1993) 119 ALR 215, 236 [79] (Gummow J).

[16] Jorden v Money (1854) 5 HL Cas 185, 214–6 (Lord Cranworth LC). See, eg, Thompson v Palmer [1933] HCA 61; (1933) 49 CLR 507; Grundt v Great Boulder Pty Gold Mines Ltd [1937] HCA 58; (1937) 59 CLR 641 (‘Grundt’). Indeed, estoppel by representation was a rule of evidence developed and applied by the Courts of Equity prior to its adoption by the Courts of Common Law as discussed in Justice Handley, above n 10, [1-004].

[17] Barclays Bank plc v Boulter [1999] UKHL 39; [1999] 1 WLR 1919, 1923 (Lord Hoffmann).

[18] See, eg, Uniform Civil Procedure Rules 2005 (NSW) pts 1415; Kernel Holdings Pty Ltd v Rothmans of Pall Mall (Aust) Pty Ltd [1991] FCA 557; (1991) 217 ALR 171, 173 (French J); Pinson v Lloyds & National Provincial Foreign Bank Ltd [1941] 2 KB 72, 75 (Scott LJ).

[19] An estoppel by representation can operate in respect of the existence (or non-existence) of rights, see, eg, Waltons Stores (1988) 164 CLR 387, 414–15, 432 (Brennan J); Azov Shipping Co v Baltic Shipping Co [1992] 2 Lloyd’s Rep 159, 173–6 (Coleman J); Cobbe v Yeoman’s Row Management Ltd [2008] UKHL 55; [2008] 1 WLR 1752, 1761 [14] (Lord Scott). In relation to estoppel by convention, see, eg, Eslea Holdings Ltd v Butts (1986) 6 NSWLR 175, 185–9 (Samuels JA, with whom Kirby P agreed); Ryledar Pty Ltd v Euphoric Pty Ltd [2007] NSWCA 65; (2007) 69 NSWLR 603, 644 [194] (Tobias JA, with whom Mason P and Campbell JA agreed); Mineralogy Pty Ltd v Sino Iron Pty Ltd [No 6] [2015] FCA 825; (2015) 329 ALR 1, 120 [759] (Edelman J); Justice Handley, above n 10, [2-013].

[20] Waltons Stores (1988) 164 CLR 387, 414.

[21] [1937] HCA 58; (1937) 59 CLR 641 (‘Grundt’). See also, Government Employees Superannuation Board v Martin (1997) 19 WAR 224; Air Tahiti Nui Pty Ltd v McKenzie (2009) 77 NSWLR 299 (‘McKenzie’); Prime Sight v Lavarello [2013] UKPC 22; [2014] AC 436 (‘Lavarello’).

[22] Con-Stan Industries of Australia Pty Ltd v Norwich Winterthur Insurance (Australia) Ltd [1986] HCA 14; (1986) 160 CLR 226, 244 (Gibbs CJ, Mason, Wilson, Brennan and Dawson JJ); Feltham, Hochberg and Leech, above n 4, ch VIII.

[23] Grundt [1937] HCA 58; (1937) 59 CLR 641, 672–3, 677, 682 (Dixon J, with whom McTiernan J agreed). Contra Latham CJ: at 656–8.

[24] Ibid 659 (Latham CJ), 677 (Dixon J).

[25] Ibid 659.

[26] Ibid 658.

[27] Ibid 658 (Latham CJ).

[28] Ibid 677.

[29] See Justice Kenneth Handley, Spencer Bower and Handley: Res Judicata (LexisNexis, 4th ed, 2009).

[30] Freeman v Cooke [1848] EngR 687; (1848) 2 Ex 654, 663; [1848] EngR 687; 154 ER 652, 656 (Parke B) (‘Freeman’); Sarat Chunder Dey v Gopal Chunder Laha (1892) 19 LR Ind App 203, 215 (Lord Shand); McKenzie (2009) 77 NSWLR 299, 310 [83], 311–12 [93]–[95] (Allsop P and Handley AJA, with whom Hodgson JA agreed).

[31] Freeman [1848] EngR 687; (1848) 2 Ex 654, 663; [1848] EngR 687; 154 ER 652, 656 (Parke B); Low v Bouverie [1891] UKLawRpCh 106; [1891] 3 Ch 82, 106 (Bowen LJ); Standard Chartered Bank Australia Ltd v Bank of China (1991) 23 NSWLR 164,

180–1 (Giles J).

[32] See text accompanying below nn 70–71.

[33] Low v Bouverie [1891] UKLawRpCh 106; [1891] 3 Ch 82, 105 (Bowen LJ); Waltons Stores (1988) 164 CLR 387, 414–5 (Brennan J); Silovi Pty Ltd v Barbaro (1988) 13 NSWLR 466, 472 (Priestley JA with whom Hope and McHugh JJA agreed); McKenzie (2009) 77 NSWLR 299, 307–8 [59]–[66] (Allsop P and Handley AJA, with whom Hodgson JA agreed).

[34] See also J D Heydon, Justice M J Leeming and P G Turner, Meagher, Gummow & Lehane’s Equity: Doctrines & Remedies (LexisNexis, 5th ed, 2014) 533 [17-180].

[35] Hood v Commonwealth [1968] VicRp 81; [1968] VR 619, 624–5 (Winneke CJ, Gowans and Menhennitt JJ); John William Smith (ed), A Selection of Leading Cases on Various Branches of the Law (Sweet & Maxwell, 13th ed, 1929) 657; J D Heydon, Cross on Evidence (LexisNexis, 10th Australian ed, 2015) 243 [5001].

[36] See, eg, Labracon Pty Ltd v Cuturich (2013) 17 BPR 32 497, 32 520 [151] (Lindsay J); Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 623–4 [153] (Gageler J); Feltham, Hochberg and Leech, above n 4, [I.4.4]–[I.4.5], [I.8.1]–[I.8.5].

[37] See, eg, Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 623–4 [153] (Gageler J); Feltham, Hochberg and Leech, above n 4, [I.4.4]–[I.4.5]; Bant and Bryan, above n 1, 450–52.

[38] See, eg, Justice Handley, above n 10, [1-09]–[1-012]; McFarlane, ‘The Limits to Estoppels’, above n 10; McFarlane, ‘Understanding Equitable Estoppel’, above n 10.

[39] Such as promissory estoppel and proprietary estoppel, and the latter can be broken down into further sub-species such as estoppel by encouragement: see, eg, Plimmer v Mayor, Councillors and Citizens Wellington (1884) 9 App Cas 699 or estoppel by acquiescence: see, eg, Ramsden v Dyson [1866] UKLawRpHL 7; (1866) 1 LR HL 129.

[40] See generally, Sidhu v Van Dyke [2014] HCA 19; (2014) 251 CLR 505, 511 [2] (French CJ, Kiefel, Bell and Keane JJ); Priestley v Priestley [2016] NSWSC 1096 (15 August 2016) [109]–[137] (White J); Thorner v Major [2009] UKHL 18; [2009] 1 WLR 776, 786 [29] (Lord Walker) (‘Thorner’); Justice Handley, above n 10, ch 11;

Ben McFarlane, The Law of Proprietary Estoppel (Oxford University Press, 2014) chs 1–2; Heydon, Leeming and Turner, above n 34, 519–27 [17-065]–[17-130].

[41] [2009] UKHL 18; [2009] 1 WLR 776.

[42] Thorner [2009] UKHL 18; [2009] 1 WLR 776, 780 [12] (Lord Scott). See also Waltons Stores (1988) 164 CLR 387, 404 (Mason CJ and Wilson J), 416, 430 (Brennan J); Giumelli v Giumelli (1999) 196 CLR 101,

111–12 [2]–[6] (Gleeson CJ, McHugh, Gummow and Callinan JJ) (‘Giumelli’); Crabb v Arun District Council [1976] 1 Ch 179, 187–8 (Lord Denning MR), 192–3 (Scarman LJ) (‘Crabb’).

See also J C Campbell, ‘When and Why a Bribe is Held on a Constructive Trust: The Method of Reasoning towards an Equitable Remedy’ (2015) 39(3) Australian Bar Review 320, 325–7.

[43] [2001] Ch 210.

[44] (1999) 196 CLR 101.

[45] [2014] HCA 19; (2014) 251 CLR 505.

[46] See generally, Waltons Stores (1988) 164 CLR 387, 404–6 (Mason CJ and Wilson J); Ashton v Pratt [2015] NSWCA 12; (2015) 88 NSWLR 281, 306–7 [140]–[141] (Bathurst CJ with whom McColl JA agreed); High Trees [1946] EWHC KB 1; [1947] 1 KB 130, 134 (Denning J); Baird Textile Holdings Ltd v Marks and Spencer plc [2001] EWCA Civ 274 (28 February 2001) [83]–[89] (Mance LJ); Justice Handley, above n 10, ch 13.

[47] See, eg, High Trees [1946] EWHC KB 1; [1947] 1 KB 130; Justice Handley, above n 10, [13-006]–[13-007]. It is unclear whether equitable estoppels, other than proprietary estoppel, can ever operate as a positive source of rights and obligations: see, eg, Waltons Stores (1988) 164 CLR 387, 404, 408 (Mason CJ and Wilson J), 416 (Brennan J); Silovi Pty Ltd v Barbaro (1988) 13 NSWLR 466, 472 (Priestley JA, with whom Hope and McHugh JJA agreed); Commonwealth v Verwayen (1990) 170 CLR 394, 413 (Mason CJ), 428–9 (Brennan J) (‘Verwayen’); Metropolitan Transit Authority v Waverley Transit Pty Ltd [1991] VicRp 14; [1991] 1 VR 181, 205–7 (Murphy, Marks and Gobbo JJ); E K Nominees Pty Ltd v Woolworths Ltd [2006] NSWSC 1172 (16 November 2006) [219]–[223], [278] (White J); Andrew Robertson, ‘Three Models of Promissory Estoppel’ (2013) 7(3) Journal of Equity 226; Ben McFarlane and Sir Philip Sales, ‘Promises, Detriment, and Liability: Lessons from Proprietary Estoppel’ (2015) 131 (October) Law Quarterly Review 610; Allison Silink, ‘Can Promissory Estoppel Be An Independent Source of Rights?’ [2015] UWALawRw 40; (2015) 40(1) The University of Western Australia Law Review 39; McFarlane, ‘Equitable Estoppel as a Cause of Action’, above n 12; or are otherwise confined in their operation and scope as defensive equities: see, eg, Combe v Combe [1952] EWCA Civ 7; [1951] 2 KB 215, 220 (Denning LJ); Bank Negara Indonesia v Hoalim [1973] 2 MLJ 3, 5 (Lord Wilberforce); Baird Textile Holdings Ltd v Marks & Spencer plc [2001] EWCA Civ 274 (28 February 2001) [38]–[39] (Sir Andrew Morritt V-C); Saleh v Romanous [2010] NSWCA 274; (2010) 79 NSWLR 453, 460–2 [62]–[79] (Handley AJA, with whom Giles JA and Sackville AJA agreed); Justice Handley, above n 10, [13-006]–[13-043]). Resolution of this debate is not required for the purposes of this article, and is not an issue that undermines the thesis presented here. On either view, an equitable estoppel creates rights (positive or negative) between the parties in response to the state of affairs existing between them.

[48] Waltons Stores (1988) 164 CLR 387, 404 (Mason CJ and Wilson J), 416, 430 (Brennan J); Giumelli (1999) 196 CLR 101, 111–12 [2]–[6] (Gleeson CJ, McHugh, Gummow and Callinan JJ); Plimmer v Mayor, Councillors and Citizens Wellington (1884) 9 App Cas 699, 714 (Sir Arthur Hobhouse); Crabb [1976] 1 Ch 179, 187–8 (Lord Denning MR), 192–3 (Scarman LJ); Thorner [2009] UKHL 18; [2009] 1 WLR 776, 780 [12] (Lord Scott). See also, Campbell, above n 42, 325–7.

[49] DHJPM Pty Ltd v Blackthorn Resources Ltd [2011] NSWCA 348; (2011) 83 NSWLR 728, 747 [75] (Meagher JA, with whom Macfarlan JA agreed); Crabb [1976] 1 Ch 179, 192–3, 195 (Scarman LJ); Gillett v Holt [2001] Ch 210, 225 (Robert Walker LJ); J C Campbell, ‘Waltons v Maher: History, Unconscientiousness and Remedy — The Minimum Equity’ (2013) 7(3) Journal of Equity 171, 187–8.

[50] Giumelli (1999) 196 CLR 101, 125 [49]–[50] (Gleeson CJ, McHugh, Gummow and Callinan JJ); Gillett v Holt [2001] Ch 210, 237–8 (Robert Walker LJ); Simon Gardner, ‘The Remedial Discretion in Proprietary Estoppel’ (1999) 115 (July) Law Quarterly Review 438; Simon Gardner, ‘The Remedial Discretion in Proprietary Estoppel — Again’ (2006) 122 (July) Law Quarterly Review 492.

[51] See, eg, Verwayen (1990) 170 CLR 394, 440 (Deane J); Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 623–4 [153] (Gageler J); Canada and Dominion Sugar [1947] AC 46, 56 (Lord Wright); Moorgate Mercantile Co Ltd v Twitchings [1976] QB 225, 241–2 (Lord Denning MR); Avon County Council v Howlett [1983] 1 WLR 605, 608 (Cumming-Bruce LJ), 611–12 (Everleigh LJ), 624–5 (Slade LJ) (‘Howlett’); Scottish Equitable plc v Derby [2001] EWCA Civ 369; [2001] 3 All ER 818, 830 [44] (Robert Walker LJ) (‘Derby’); National Westminster Bank [2001] EWCA Civ 970; [2002] QB 1286, 1306 [48] (Potter LJ), 1309 [60] (Clarke LJ), 1310–11 [67] (Peter Gibson LJ). See also Feltham, Hochberg and Leech, above n 4, [I.4.1]–[I.4.5]; Bant and Bryan, above n 1, 449–52.

[52] In relation to common law estoppels, see Waltons Stores (1988) 164 CLR 387, 404 (Mason CJ and Wilson J); Verwayen (1990) 170 CLR 394, 409–10, 413 (Mason CJ); Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 599 [85]–[86] (Hayne, Crennan, Kiefel, Bell and Keane JJ), 622–4 [149]–[154] (Gageler J). In relation to equitable estoppels, see: Waltons Stores (1988) 164 CLR 387, 401 (Mason CJ and Wilson J), 418–9, 421–3 (Brennan J); Verwayen (1990) 170 CLR 394, 409–10, 412, 417 (Mason CJ), 429–30 (Brennan J), 454 (Dawson J), 476 (Toohey J), 487 (Gaudron J), 501, 504 (McHugh J); McFarlane, above n 40, ch 7; Andrew Robertson, ‘The Reliance Basis of Proprietary Estoppel Remedies’ (2008) 72 Conveyancer and Property Lawyer 295.

[53] Lockyer v Ferryman (1877) 2 App Cas 519, 530 (Lord Blackburn). See further Port of Melbourne Authority v Anshun Pty Ltd [1981] HCA 45; (1981) 147 CLR 589, 597 (Gibbs CJ, Mason and Aickin JJ); Dow Jones & Co Inc v Gutnick (2002) 210 CLR 575, 604 [36] (Gleeson CJ, McHugh, Gummow and Hayne JJ); Carl Zeiss Stiftung v Rayner & Keeler Ltd [No 2] [1967] 1 AC 853, 909 (Lord Reid), 935 (Lord Guest).

[54] Rogers v The Queen [1994] HCA 42; (1994) 181 CLR 251, 273–4 (Deane and Gaudron JJ).

[55] Hudson, ‘The True Purpose of Estoppel by Representation’, above n 8; Hudson, ‘Estoppel by Representation as a Defence to Unjust Enrichment’, above n 8.

[56] Knights v Wiffen (1870) 5 LR QB 660, 666 (Mellor J); Burkinshaw v Nicolls (1878) 3 App Cas 1004, 1026 (Lord Blackburn); Re Exchange Securities & Commodities Ltd (in liq) [1988] 1 Ch 46, 54 (Harman J); C Blackburn, A Treatise on the Effect of the Contract of Sale on the Legal Rights of Property and Possession in Goods, Wares, and Merchandise (Benning, 1845) 163, cited with approval in M’Cance v London & North Western Railway Co (1864) 3 Hurl & C 343, 345 (Williams J); Lavarello [2013] UKPC 22; [2014] AC 436, 448 [39] (Lord Toulson for the Board).

[57] Burkinshaw v Nicolls (1878) 3 AC 1004, 1026.

[58] Lavarello [2013] UKPC 22; [2014] AC 436, 447 [35] (Lord Toulson for the Board). See also Feltham, Hochberg and Leech, above n 4, [VIII.8.1].

[59] Lavarello [2013] UKPC 22; [2014] AC 436, 450 [46] (Lord Toulson for the Board). See also: at 449–50 [45].

[60] Blair v Curran [1939] HCA 23; (1939) 62 CLR 464, 531–2 (Dixon J).

[61] See above n 52.

[62] Verwayen (1990) 170 CLR 394, 411–13 (Mason CJ), 500–1 (McHugh J); Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 622–5 [149]–[155] (Gageler J); Feltham, Hochberg and Leech, above n 4, [I.8.1]–[I.8.5].

[63] See, eg, Waltons Stores (1988) 164 CLR 387, 404 (Mason CJ and Wilson J); Verwayen (1990) 170 CLR 394, 409–10, 415 (Mason CJ); Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 599 [85]–[86] (Hayne, Crennan, Kiefel, Bell and Keane JJ), 622–4 [149]–[154] (Gageler J); Crown Melbourne [2016] HCA 26; (2016) 90 ALJR 770, 781 [39] (French CJ, Kiefel and Bell JJ), 796 [139]–[140] (Keane J); Gillett v Holt [2001] Ch 210, 232–3 (Robert Walker LJ).

[64] Grundt [1937] HCA 58; (1937) 59 CLR 641, 674 (Dixon J). See also Thompson v Palmer [1933] HCA 61; (1933) 49 CLR 507, 547 (Dixon J).

[65] Grundt [1937] HCA 58; (1937) 59 CLR 641, 674.

[66] See, eg, Hasler v Singtel Optus Pty Ltd [2014] NSWCA 266; (2014) 87 NSWLR 609, 625 [67] (Leeming JA); Paciocco v Australia & New Zealand Banking Group Ltd (2015) 236 FCR 199, 234 [103] (Allsop CJ, with whom Besanko and Middleton JJ agreed).

[67] Grundt [1937] HCA 58; (1937) 59 CLR 641, 674 (Dixon J).

[68] Ibid 674.

[69] Ibid 675.

[70] Ibid 674–5 (Dixon J).

[71] Ibid 659 (Latham CJ), 677 (Dixon J).

[72] See, eg, Greenwood v Martins Bank Ltd [1933] AC 51, 57 (Lord Tomlin), cited with approval in Thompson v Palmer [1933] HCA 61; (1933) 49 CLR 507, 520 (Rich J); Steria Ltd v Hutchison [2006] EWCA Civ 1551 (24 November 2006) [93] (Neuberger LJ); Franklin v Manufacturers Mutual Insurance Ltd [1935] NSWStRp 62; (1935) 36 SR (NSW) 76, 82 (Jordan CJ); Feltham, Hochberg and Leech, above n 4, [I.3.2], [V.5.1]–[V.5.18]; Justice Handley, above n 10, [1-008], [5-016]–[5-018].

[73] Kelly v Fraser [2012] UKPC 25; [2013] 1 AC 450, 460 [17] (Lord Sumption for the Board).

[74] PW & Co v Milton Gate Investments Ltd [2004] Ch 142, 181 [149] (Neuberger J).

[75] Greer v Kettle [1938] AC 156, 170–1 (Lord Maugham); Feltham, Hochberg and Leech, above n 4, [I.2.10].

[76] See above n 52.

[77] See above n 64 and accompanying text.

[78] Sidhu v Van Dyke [2014] HCA 19; (2014) 251 CLR 505, 522–3 [58], 527–8 [77] (French CJ, Kiefel, Bell and Keane JJ); Crown Melbourne [2016] HCA 26; (2016) 90 ALJR 770, 797 [146] (Keane J), 810–11 [217] (Nettle J); Arfaras v Vosnakis (2016) 18 BPR 35 819, 35 836–7 [111]–[114] (Ward JA, with whom Beazley P and Simpson JA agreed); Campbell, above n 49, 187–8; Amalgamated Investment & Property Co Ltd (in liq) v Texas Commerce International Bank Ltd [1982] 1 QB 84, 104–5 (Goff J); Gillett v Holt [2001] Ch 210, 232 (Robert Walker LJ).

[79] Olsson v Dyson [1969] HCA 3; (1969) 120 CLR 365, 379 (Kitto J); Riches v Hogben [1985] 2 Qd R 292, 300–1 (McPherson J); Sidhu v Van Dyke [2014] HCA 19; (2014) 251 CLR 505, 522–3 [58] (French CJ, Kiefel, Bell and Keane JJ); Amalgamated Investment & Property Co Ltd (in liq) v Texas Commerce International Bank Ltd [1982] 1 QB 84, 104–5 (Goff J).

[80] Sullivan v Sullivan (2006) 13 BPR 24 755, 24 758 [20] (Handley JA); Donis v Donis [2007] VSCA 89; (2007) 19 VR 577, 582 [19] (Nettle JA).

[81] Ashton v Pratt [2015] NSWCA 12; (2015) 88 NSWLR 281, 307 [142] (Bathurst CJ, with whom McColl JA agreed) (citations omitted). See, eg, Giumelli (1999) 196 CLR 101, 125 [48] (Gleeson CJ, McHugh, Gummow and Callinan JJ); Sidhu v Van Dyke [2014] HCA 19; (2014) 251 CLR 505, 522–3 [58], 527–8 [75]–[78], 530 [85] (French CJ, Kiefel, Bell and Keane JJ); Arfaras v Vosnakis (2016) 18 BPR 35 819,

35 836–7 [111]–[114] (Ward JA, with whom Beazley P and Simpson JA agreed); Gillett v Holt [2001] Ch 210, 235–8 (Robert Walker LJ); Jennings v Rice [2003] EWCA Civ 159; [2003] 1 P & CR 100, 106 [21], 111 [36] (Aldous LJ, with whom Mantell and Robert Walker LJJ agreed); Thorner [2009] UKHL 18; [2009] 1 WLR 776,

784–5 [20]–[21] (Lord Scott); James Edelman, ‘Remedial Certainty or Remedial Discretion in Estoppel after Giumelli?’ (1999) 15(2) Journal of Contract Law 179, 189; Heydon, Leeming and Turner, above n 34, 542–3 [17-285].

[82] See, eg, Giumelli (1999) 196 CLR 101; Sidhu v Van Dyke [2014] HCA 19; (2014) 251 CLR 505; Gillett v Holt [2001] Ch 210; Thorner [2009] UKHL 18; [2009] 1 WLR 776, 796 [66] (Lord Walker).

[83] [2015] NSWCA 12; (2015) 88 NSWLR 281, 307 [142] (with whom McColl JA agreed) (citations omitted).

[84] Sidhu v Van Dyke [2014] HCA 19; (2014) 251 CLR 505, 529–30 [83]–[85] (French CJ, Kiefel, Bell and Keane JJ); Sledmore v Dalby [1996] EWCA Civ 1305; [1996] 72 P & CR 196, 208 (Hobhouse LJ); Jennings v Rice [2003] EWCA Civ 159; [2003] 1 P & CR 100, 106 [21], 111 [36] (Aldous LJ, with whom Mantell and Robert Walker LJJ agreed).

[85] See above n 47.

[86] Bant and Bryan, above n 1, 429.

[87] Ibid.

[88] National Westminster Bank [2001] EWCA Civ 970; [2002] QB 1286, 1301–2 [35] (Potter LJ); Fung and Ho, above n 4, 18.

[89] National Westminster Bank [2001] EWCA Civ 970; [2002] QB 1286, 1301–2 [35] (Potter LJ); Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 623–4 [153] (Gageler J).

[90] [2012] UKPC 25; [2013] 1 AC 450, 460 [17] (Lord Sumption for the Board).

[91] This is particularly so when estoppel by representation is raised as a defence to a claim for restitution of a mistaken payment: see, eg, TRA Global Pty Ltd v Kebakoska [2011] VSC 480; (2011) 209 IR 453; Citigroup Pty Ltd v National Australia Bank Ltd [2012] NSWCA 381; (2012) 82 NSWLR 391; Howlett [1983] 1 WLR 605; Derby [2001] EWCA Civ 369; [2001] 3 All ER 818; National Westminster Bank [2001] EWCA Civ 970; [2002] QB 1286. See generally, Graham Virgo, The Principles of the Law of Restitution (Oxford University Press, 3rd ed, 2015) 666–74; Andrew Burrows, The Law of Restitution (Oxford University Press, 3rd ed, 2011) 550–8; Justice Handley, above n 10, [5-027]–[5-028]; C Mitchell, P Mitchell and S Watterson, Goff & Jones: The Law of Unjust Enrichment (Sweet & Maxwell, 9th ed, 2016) ch 30.

[92] Giumelli (1999) 196 CLR 101, 111–12 [2]–[6] (Gleeson CJ, McHugh, Gummow and Callinan JJ); Crabb [1976] 1 Ch 179, 187–188 (Lord Denning MR), 192–193 (Scarman LJ).

[93] Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 623–4 [153] (Gageler J); Howlett [1983] 1 WLR 605, 608 (Cumming-Bruce LJ), 611–12 (Everleigh LJ), 624–5 (Slade LJ); Derby [2001] EWCA Civ 369; [2001] 3 All ER 818, 830 [44] (Robert Walker LJ); National Westminster Bank [2001] EWCA Civ 970; [2002] QB 1286, 1306 [48] (Potter LJ), 1309 [60] (Clarke LJ), 1310–11 [67] (Peter Gibson LJ); Justice Handley, above n 10, [5-029]–[5-034]; Feltham, Hochberg and Leech, above n 4, [I.4.5]–[I.4.6], [I.8.5]; Bant and Bryan, above n 1, 449-452; Virgo, above n 91, 700.

[94] Australian Financial Services & Leasing [2014] HCA 14; (2014) 253 CLR 560, 624 [153] (Gageler J). See also, Canada and Dominion Sugar [1947] AC 46, 56 (Lord Wright).

[95] See above n 91. It has also been suggested that in the context of claims for restitution of a mistaken payment, estoppel by representation may have been ‘subsumed in the defence of change of position’: Citigroup Pty Ltd v National Australia Bank Ltd [2012] NSWCA 381; (2012) 82 NSWLR 391, 418 [130] (Barrett JA).

See also Hudson, ‘Estoppel by Representation as a Defence to Unjust Enrichment’, above n 8 for arguments against these proposals.

[96] Howlett [1983] 1 WLR 605, 608 (Cumming-Bruce LJ), 611–12 (Everleigh LJ), 624–5 (Slade LJ); Derby [2001] EWCA Civ 369; [2001] 3 All ER 818, 830 [44] (Robert Walker LJ); National Westminster Bank [2001] EWCA Civ 970; [2002] QB 1286, 1306 [48] (Potter LJ), 1309 [60] (Clarke LJ), 1310–11 [67] (Peter Gibson LJ). This exception seems to be limited to cases where estoppel by representation is raised as a defence to a claim to recover a mistaken payment: Kaupthing Singer & Friedlander Ltd (in administration) v UBS AG [2014] EWHC 2450 (Comm) (18 July 2014) [108]–[110] (Smith J).

[97] Low v Bouverie [1891] UKLawRpCh 106; [1891] 3 Ch 82, 106 (Bowen LJ); The Western Australian Insurance Co Ltd v Dayton [1924] HCA 58; (1924) 35 CLR 355, 375 (Isaacs ACJ); Legione [1983] HCA 11; (1983) 152 CLR 406, 435–436 (Mason and Deane JJ).

[98] Freeman [1848] EngR 687; (1848) 2 Ex 654, 663; [1848] EngR 687; 154 ER 652, 656 (Parke B); Sarat Chunder Dey v Gopal Chunder Laha (1892) 19 LR Ind App 203, 215 (Lord Shand).

[99] Thompson v Palmer [1933] HCA 61; (1933) 49 CLR 507, 547 (Dixon J); Newbon v City Mutual Life Assurance Society Ltd [1935] HCA 33; (1935) 52 CLR 723, 734 (Rich, Dixon and Evatt JJ); Grundt [1937] HCA 58; (1937) 59 CLR 641, 675–6 (Dixon J); Verwayen (1990) 170 CLR 394, 444 (Deane J).

[100] Freeman [1848] EngR 687; (1848) 2 Ex 654, 663; [1848] EngR 687; 154 ER 652, 656 (Parke B); Bant and Bryan, above n 1, 440–44.

[101] See, eg, Low v Bouverie [1891] UKLawRpCh 106; [1891] 3 Ch 82 (B’s assumption not reasonably induced by A’s representation); Steria Ltd v Hutchison [2006] EWCA Civ 1551 (24 November 2006)

(no representation, reliance or detriment); Thompson v Palmer [1933] HCA 61; (1933) 49 CLR 507, 547 (Dixon J) (no substantive detriment).

[102] (1854) 5 HL Cas 185, 212.

[103] Greer v Kettle [1938] AC 156, 170–171 (Lord Maugham); Lavarello [2013] UKPC 22; [2014] AC 436, 448–51

[41]–[51] (Lord Toulson for the Board).

[104] Sarat Chunder Dey v Gopal Chunder Laha (1892) 19 LR Ind App 203, 215 (Lord Shand); McKenzie (2009) 77 NSWLR 299, 310 [83], 311–12 [93]–[95] (Allsop P).

[105] Smith v Hughes (1871) 6 LR QB 597, 603 (Cockburn CJ), 607 (Blackburn J); Bell v Lever Brothers Ltd [1931] UKHL 2; [1932] AC 161, 217–22 (Lord Atkin); Sir Guenter Treitel, ‘Contract: In General’ in Andrew Burrows (ed), English Private Law (Oxford University Press, 2nd ed, 2007) 623, 677–87 [8132]–[8158].

[106] Greer v Kettle [1938] AC 156, 170–71 (Lord Maugham); Lavarello [2013] UKPC 22; [2014] AC 436, 448–51 [41]–[51] (Lord Toulson for the Board).

[107] Howell v Falmouth Boat Construction Co Ltd [1951] AC 837, 845 (Lord Simonds), 849 (Lord Normand). See also Greg Weeks, ‘Estoppel and Public Authorities: Examining the Case for an Equitable Remedy’ (2010) 4(3) Journal of Equity 247.

[108] Kok Hoong v Leong Cheong Kweng Mines Ltd [1964] AC 993, 1015 (Viscount Radcliffe).

[109] Lavarello [2013] UKPC 22; [2014] AC 436, 448–9 [41] (Lord Toulson for the Board).

[110] Legione [1983] HCA 11; (1983) 152 CLR 406, 432 (Mason and Deane JJ); Waltons Stores (1988) 164 CLR 387,

398–9 (Mason CJ and Wilson J), 415 (Brennan J), 459 (Gaudron J); High Trees [1946] EWHC KB 1; [1947] 1 KB 130,

134 (Denning); Roebuck v Mungovin [1994] 2 AC 224, 235 (Lord Browne-Wilkinson); Feltham, Hochberg and Leech, above n 4, [II.4.1].

[111] Ibid; see also, Jorden v Money (1854) 5 HL Cas 185, 214–16, 226–7 (Lord Cranworth LC); Maddison v Alderson (1883) 8 App Cas 467, 473 (Lord Selborne LC); The Citizens’ Bank of Louisiana v The First National Bank of New Orleans [1873] UKLawRpHL 16; (1873) LR 6 HL 352, 360 (Lord Selborne LC); Chadwick v Manning [1896] UKLawRpAC 3; [1896] AC 231, 238–9 (Lord Macnaghten).

[112] Ibid.

[113] See, eg, High Trees [1946] EWHC KB 1; [1947] 1 KB 130.

[114] See also, Justice Handley, above n 10, [2-012].

[115] Verwayen (1990) 170 CLR 394, 412 (Mason CJ); Andrew Robertson, ‘Estoppels and Rights-Creating Events: Beyond Wrongs and Promises’ in Jason W Neyers, Richard Bronaugh and Stephen G A Pitel (eds), Exploring Contract Law (Hart Publishing, 2009) 199, 216; Feltham, Hochberg and Leech, above n 4, [II.6.3].


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