By Ian Cobain, Daily Mail

Tortured by British soldiers? In captivity? In London? The idea seems incredible.

The German SS officer was fighting to save himself from the gallows for a terrible war crime and might say anything to escape the noose. But Fritz Knöchlein was not lying in 1946 when he claimed that, in captivity in London, he had been tortured by British soldiers to force a confession out of him.