The following principles apply to a proceeding in deciding whether a public or other authority has a duty or has breached a duty—
(a) the functions required to be exercised by the authority are limited by the financial and other resources that are reasonably available to the authority for the purpose of exercising the functions;
(b) the general allocation of financial or other resources by the authority is not open to challenge;
(c) the functions required to be exercised by the authority are to be decided by reference to the broad range of its activities (and not merely by reference to the matter to which the proceeding relates);
(d) the authority may rely on evidence of its compliance with its general procedures and any applicable standards for the exercise of its functions as evidence of the proper exercise of its functions in the matter to which the proceeding relates.