Tied to a Channel 4 television series in three one-hour parts, this is the story of the breaking of the Enigma code at Bletchley Park during World War II. That remarkable feat - breaking a code that the Germans believed to be unbreakable - was to play a major part in the outcome of the war. The book draws on official files and the testimonies of survivors to tell the story of a unique institution and the people who worked there. Examples designed to be intelligible to the layman are provided to illustrate how the code worked and how it was deciphered.