The first Soviet atomic test in 1949. Klaus Fuchs, after his release from prison in the UK, reading The Times in East Germany in 1960

Between 1941 and 1950 the German physicist Klaus Fuchs handed over British and American nuclear secrets to Stalin’s Soviet Union. It was the most effective act of espionage in history. He showed Moscow how to build first the atomic bomb, then the much more powerful hydrogen bomb. For this crime he served just nine years in prison, in Brixton and Wakefield. In America in 1953, two Soviet spies whose disclosures were much less damaging, Julius and Ethel Rosenberg — who had link to Fuchs — were executed.

Fuchs had confessed and his trial lasted just 90 minutes. The “hanging” judge Rayner Goddard would certainly have liked to kill him — one of his clerks claimed he had an orgasm whenever he passed a death sentence