He was detained for a short time at the concentration camp at Dachau, but soon after his release he left Germany in 1939 for England and has resided here ever since.

This stemmed from the double taxation conventions concluded between the UK and Germany, later incorporated into English law.

In 1968, the German Federal Constitutional Court decided that the 1941 decree was void ab initio, but that decision had no retrospective effect.

Mr Oppenheimer became entitled to apply for reinstatement as a German national and did so, with the status being granted automatically.

He subsequently benefited from the dual nationality provision in the double taxation agreement, so the case only covered his status and pension from 1953–54 to 1967–68.

The logic behind this is the subject of an article written by the legal commentator J. G. Merrills, the Edward Bramley Professor of Law at Sheffield University.

"... the decision turned ultimately upon an issue which the English courts treat as a question of fact, namely the appellant's nationality in German law.

"[12] Oppenheimer confirms the English courts' tendency to take their international law from textbooks instead of from the primary sources.

Yet there is no shortage of material from which principles of customary international law relating to non-discrimination and deprivation of nationality might be derived.

A review by the House of Lords of some of this material would have been welcome, as both a clear demonstration of the grounding of the decision in contemporary ideals and as a contribution to the development of customary international law… The work relied on in Oppenheimer was the second edition of Wolff's Private International Law, published in 1950.The case is often cited for the quote of Lord Cross in relation to the repugnance of the English courts for Nazi era confiscation laws.

However, there are other English decisions where similar laws have been broadly recognised as effective to a certain degree (Frankfurther v W L Exner Ltd [1947] Ch 629 and Bohm v Czerny (1940) 190 LT Jo 54).