House of Lords
There has long been a desire among restitution lawyers to escape from the unfortunate effects of the so-called rule that money is only recoverable at common law on the ground of failure of consideration where the failure is total, by reformulating the rule upon a more principled basis; and signs that this will in due course be done are appearing in judgments throughout the common law world, as appropriate cases arise for decision. It is fortunate however that, in the present case, thanks (I have no doubt) to the admirable researches of counsel, a line of authority was discovered which had escaped the attention of the scholars who work in this field. 683 This line of authority was concerned with contracts for annuities which were void if certain statutory formalities were not complied with. They were not therefore concerned with contracts void by reason of the incapacity of one of the parties. Even so, they were concerned with cases in which payments had been made, so to speak, both ways; and the courts had to decide whether they could, in such circumstances, do justice by restoring the parties to their previous positions. They did not hesitate to do so, by ascertaining the balance of the account between the parties, and ordering the repayment of the balance. Moreover the form of action by which this was achieved was the old action for money had and received - what we nowadays call a personal claim in restitution at common law. With this precedent before him, Hobhouse J. felt free to make a similar order in the present case; and in this he was self-evidently right.
The most serious problem which has remained in this connection is the theoretical question whether recovery can here be said to rest upon the ground of failure of consideration. Hobhouse J. thought not. He considered that the true ground in these cases, where the contract is void, is to be found in the absence, rather than the failure, of consideration; and in this he was followed by the Court of Appeal. This had the effect that the courts below were not troubled by the question whether there had been a total failure of consideration.
The approach so adopted may have found its origin in the idea, to be derived from a well known passage in the speech of Viscount Simon L.C. in Fibrosa Spolka Akcyjna v. Fairbairn Lawson Combe Barbour Ltd.  A.C. 32, 48, that a failure of consideration only occurs where there has been a failure of performance by the other party of his obligation under a contract which was initially binding. But the concept of failure of consideration need not be so narrowly confined. In particular it appears from the annuity cases themselves that the courts regarded them as cases of failure of consideration; and concern has been expressed by a number of restitution lawyers that the approach of Hobhouse J. is contrary to principle and could, if accepted, lead to undesirable consequences: see Professor Birks, "No Consideration: Restitution after Void Contracts" (1993) 23 W.A.L.R. 195; Mr. W. J. Swadling, "Restitution for No Consideration"  R.L.R. 73 and Professor Burrows, "Swaps and the Friction between Common Law and Equity"  R.L.R. 15. However since there is before your Lordships no appeal from the decision that the bank was entitled to recover the balance of the payments so made in a personal claim in restitution, the precise identification of the ground of recovery was not explored in argument before the Appellate Committee. It would therefore be inappropriate to express any concluded view upon it. Even so, I think it right to record that there appears to me to be considerable force in the criticisms which have been expressed; and I shall, when considering the issues on this appeal, bear in mind the possibility that it may be right to regard the ground of recovery as failure of consideration.684
One would expect to find, in any developed system of law, a comprehensive and reasonably simple set of principles by virtue of which the courts have power to award interest. Since there are circumstances in which the interest awarded should take the form of compound interest, those principles should specify the circumstances in which compound interest, as well as simple interest, may be awarded; and the power to award compound interest should be available both at law and in equity. Nowadays, especially since it has been established (see National Bank of Greece S.A. v. Pinios Shipping Co. No. 1  1 A.C. 637) that banks may, by the custom of bankers, charge compound interest upon advances made by them to their customers, one would expect to find that the principal cases in which compound interest may be awarded would be commercial cases.
Sadly, however, that is not the position in English law. Unfortunately, the power to award compound interest is not available at common law. The power is available in equity; but at present that power is, for historical reasons, exercised only in relation to certain specific classes of claim, in particular proceedings against trustees for an account. An important - I believe the most important - question in the present case is whether that jurisdiction should be developed to apply in a commercial context, as in the present case.
From these cases it can be seen that compound interest may be awarded in cases where the defendant has wrongfully profited, or may be presumed to have so profited, from having the use of another person's money. The power to award compound interest is therefore available to achieve justice in a limited area of what is now seen as the law of restitution, viz. where the defendant has acquired a benefit through his wrongful act (see Goff & Jones, The Law of Restitution, 4th ed. (1993), pp. 632 et seq.; Birks, An Introduction to the Law of Restitution, pp. 313 et seq.; Burrows, The Law of Restitution (1993), pp. 403 et seq.). The general question arises whether the jurisdiction must be kept constrained in this way, or whether it may be permitted to expand so that it can be exercised to ensure that full justice can be done elsewhere in that rubric of the law. The particular question is whether the jurisdiction can be exercised in a case such as the present in which the council has been ordered to repay the balance of the bank's money on the ground of unjust enrichment, in a personal claim at common law.
This reasoning is logical, assuming the restricted nature of the equitable jurisdiction to award compound interest. But if, as Lord Brandon in President of India v. la Pintada Compania Navigacion S.A.  A.C. 104, 116 stated, the jurisdiction is founded upon the demands of justice, it is difficult to see the sense of the distinction which Hobhouse J. felt compelled to draw. It seems strange indeed that, just because the power to trace property has ceased, the court's jurisdiction to award compound interest should also come to an end. For where the claim is based upon the unjust enrichment of the defendant, it may be necessary to have power to award compound interest to achieve full restitution, i.e. to do full justice, as much where the plaintiff's claim is personal as where his claim is proprietary in nature. Furthermore, I know of no authority which compelled Hobhouse J. to hold that he had no jurisdiction to award compound interest in respect of the personal claim in equity in the case before him.