Anybody with even the slightest appetite for the history of the Second World War is aware of the Enigma machine, a fiendishly complicated mechanism the Germans devised for their top-secret communications. The hero of the story was Alan Turing, a polymathic genius of the highest order. Turing received substantial help from three Polish mathematicians who had broken a version of the code in the early 1930s. The code-breaking project, at the famous Bletchley Park, went under the beautiful name — for a spy story — Ultra.
