A.  Introduction

  In its §142(1) the American Restatement of the Law of Restitutionprovides that \"[t]he right of a person to restitution from another because of a benefit received is terminated or diminished if, after the receipt of the benefit, circumstances have so changed that it would be inequitable to require the other to make full restitution.\" The notion that the recipient of an unjustified benefit must in principle return not more than the enrichment that has actually \"survived\" in his hands, is not only fundamental to the American law of restitution, but can also be found in English and German law.

  In the seminal, 18th Century case of Moses v. Macferlan, decided by the House of Lords, the highest Court in the United Kingdom, Lord Mansfield held, that the defendant to a restitutionary claim \"may defend himself by every thing which [shows] that the plaintiff, ex aequo et bono, is not entitled to the whole of his demand, or to any part of it.\" This can be interpreted as an early hint at the so-called defence of \"change of position.\" In Germany, a similar principle, the Wegfall der Bereicherung (literally \"cessation of the enrichment\" but used to indicate the \"change of position\" defence), is enshrined in §818 III of the Bürgerliches Gesetzbuch (BGB – Civil Code), which provides, in short, that the obligation to make restitution is excluded to the extent that the recipient of the benefit is no longer enriched.

  This essay will make a comparison of the application of the defence in Germany and England. As the first part of the paper (B.), a brief outline of the restitutionary concepts in both countries, will show, this is especially interesting given the fact that the young English law of restitution is still \"under construction\" whereas German courts have applied their law for more than 100 years. The following chapter (C.) will try to...