22 As Mr McManamey submitted, the law with respect to restitution and the defence of change of position is in a developing state. In the passage immediately following the broad statement of principle for which he contends the majority make reference to the scope of the defence in Canada and the United States:
"[T]he defence operates in different ways but the common element in all cases is the requirement that the defendant point to expenditure or financial commitment which can be ascribed to the mistaken payment. In Canada and in some United States decisions, the defendant has been required to point to specific expenditure being incurred because of the payment. Other cases in the United States allow a wider scope to the defence, such that a defendant can rely upon it even though he or she cannot precisely identify the expenditure caused by the mistaken payments."
23 The appellant does not point to expenditure or financial commitment which might be ascribed to the award payments. He relies on the detriment that he made no claim to payment from the Department of Social Security. I have been able to locate few authorities which support the proposition that a detriment, other than the expenditure of the monies mistakenly paid (on items other than ordinary living expenses) constitutes a change of position for the purpose of the defence.
24 In The Council of the City of Sydney v Burns Philp Trustee Company Ltd (In Liquidation) & Anor (unreported, NSWSC, Com D, 13 November 1992) Rogers CJ Com D considered the scope of the defence of change of position in the light of the decision in David Securities which had just been handed down. In that case the provisions of a lease between the Council as lessor and the Trustee Company as lessee provided that rent should be determined as a fixed percentage of the "unimproved land value" of the premises. In the event that the concept of "unimproved land value" was abandoned in the Valuation of Land Act a clause in the lease made provision for the parties to appoint a valuer to determine the valuation of the land. The concept of "unimproved land value" was abandoned. The Valuer General thereafter issued assessments as to the "land value" of the premises. Both parties to the lease acted for a number of years on the assumption that the latter was synonymous with "unimproved land value". Giles J in related proceedings found this assumption to be wrong. The Trustee Company brought a cross claim for recovery of overpayments of rent. Rogers CJ Com D accepted that the Council had changed its position to its detriment by not obtaining a private valuation. This entitled the Council to defeat the prima facie right to restitution to the extent of the detriment suffered by reason of that change of position (p.21).
25 In Killham v Banque Nationale de Paris (unreported, Supreme Court of Victoria, Com D, unreported, 28 June 1994) Hedigan J considered that the defendant bank would have a defence to a claim in restitution against it arising out of its assignment of its security. His Honour said this:
"Firstly, the assignment of the debenture itself constituted some alteration in position because the bank gave up its security. That security, in my judgment, must have at least realised, if exercised, the amount of the overpayment namely approximately $244,000. … Its change of position in that respect was that instead of exercising its powers under the debenture, which I conclude would have enabled it to recover its debt, it would, if the plaintiff succeeded, be obliged to return the overpayment. In my judgment this constitutes a change of position with detriment. It has never been argued by the plaintiff that the monies were not lawfully due to the bank."
26 It should be noted that his Honour's observations in this regard were obiter. In the event, the plaintiff's claim in that case failed.
27 In Morgan Guaranty Trust Co of New York v Outerbridge (1990) 66 DLR (4th) p.517, Osborne J in the Ontario High Court of Justice considered the change of position defence in a case in which the defendant's bank had mistakenly credited the sum of $150,000 to his account. The defendant was a solicitor. He believed that the sum had been paid into his account on behalf of a client. Acting on the strength of that belief he had handed over his files with respect to that client to new counsel believing that his account had been paid in full. Osborne J reviewed the authorities concerning the defence of change of position. In particular, he referred to the judgment of Goff J in Barclays Bank Ltd v W J Simms Son & Cooke (Southern) Ltd [1979] 3 All ER 522 at 535 together with a number of Canadian authorities and concluded (at 551):
"[I]f the defendant has changed his position so that it would be inequitable to require him to make restitution, then restitution will not be ordered."