Subject to any orders of the Tribunal, an involuntary patient admitted to an SMHU under section 63 may be detained there until –

(a) the end of the period of detention determined under section 64(1) (or as extended under section 64(2) ); or

(b) if the Chief Psychiatrist arranges for the transfer of the patient under section 64(5) , the end of the 24-hour period immediately after the arrangements have been made; or

(c) if the patient is subject to an assessment order, the assessment order expires or is discharged; or

(d) if the patient is subject to a treatment order, the treatment order expires or is discharged –

whichever occurs first.