UNJUST ENRICHMENT IN ENGLAND AND WALES
The principal event of the past year is the decision of the UK Supreme Court in Test Claimants in the FII Group Litigation v HMRC § 85, which joins the triptych of Investment Trust Companies (in liq) v HMRC  UKSC 29;  AC 275;  RLR §212, Littlewoods Ltd v
HMRC  UKSC 70;  AC 869;  RLR §214 and Prudential Assurance Co Ltd v
HMRC  UKSC 39;  AC 929;  RLR §216 in constraining the scope and extent of restitutionary liabilities at the heady interface of unjust enrichment, EU law, taxation and limitation of actions. Having repudiated Sempra Metals Ltd (formerly Metallgesellschaft Ltd) v IRC  UKHL 34;  1 AC 561 in those cases, in FII the team of Lord Reed and Lord Hodge set about Kleinwort Benson Ltd v Lincoln City Council  2 AC 349 and Deutsche Morgan Grenfell Group Plc v IRC  UKHL 49;  1 AC 558, undermining, probably fatally, much of the reasoning in the former, and disapproving the latter. Notably their joint judgment observed (at ):
“courts, including this court, do not often overturn settled rules of law, and in considering whether to do so they attach particular importance to the security of settled transactions. The decisions in Kleinwort Benson and Sempra Metals were exceptional in their readiness to overturn centuries of authority, as the House of Lords enthusiastically adopted the theory of unjust enrichment. Those decisions were criticised by this court in Prudential at para.63 because of their disregard of the need for judicial development of the law to be justifiable by reference to existing legal principles. Normally, as was stated in a recent judgment of this court, ‘[i]n order to preserve legal certainty, judicial developments of the common law must … be based on established principles, building on them incrementally rather than making the more dramatic changes which are the prerogative of the legislature’: R (Elgizouli) v Secretary of State for the Home Department  UKSC 10;  2 WLR 857, .”
That signals that we have moved in recent apex appellate authorities a long way from the expansionist approach to the development of the law in the first two decades following the decisive recognition of unjust enrichment 30 years ago in Lipkin Gorman v Karpnale Ltd  2 AC 548. A noticeable theme of the year is the assertion of the distinctiveness of equitable principles from unjust enrichment (Ali v Dinc § 81 and Byers v Samba Financial Group § 84).