Enigma
Their task was to crack the ingenious Enigma cipher used for high-level Nazi communications. Though Polish intelligence had given the British a copy of the Enigma machine in July 1939, the settings of the machine were changed continually, and each day the German operators had some 159,000,000,000,000,000,000 possibilities from which to choose. Unravelling the code was indeed a daunting job for the Bletchley team and the fledgling computer they managed to construct.
John Benton
Secret Intelligence
ENIGMA Cert. 15 Director: Michael Apted
The fascinating story of the code-breakers who worked at Bletchley Park during WWII remained totally unknown to the public until the mid-1970s.