During the Russian revolution, the mathematical physicist Igor Tamm was seized by anti-communist vigilantes at a village near Odessa where he had gone to barter for food. They suspected he was an anti-Ukrainian communist agitator and dragged him off to their leader.
Asked what he did for a living, he said he was a mathematician. The sceptical gang leader began to finger the bullets and grenades slung round his neck. ‘All right,’ he said, ‘calculate the error when the Taylor series approximation to a function is truncated after n terms. Do this and you will go free. Fail and you will be shot.’ Tamm slowly calculated the answer in the dust with his quivering finger. When he had finished, the bandit cast his eye over the answer and waved him on his way.
Tamm won the 1958 Nobel prize for physics but he never did discover the identity of the unusual bandit leader.
