Government Code and Cypher School
The British codebreaking agency of Bletchley Park and the forerunner of GCHQ
Overview
Formed in 1919 from the naval codebreakers of Room 40 and their army counterparts, the Government Code and Cypher School worked on diplomatic codes between the wars and moved to Bletchley Park in Buckinghamshire in 1939. There it grew to close to 10,000 people by 1945, most of them women, attacking German Enigma and Lorenz ciphers as well as Italian and Japanese systems to produce the intelligence known as Ultra. Alan Turing and Gordon Welchman designed its codebreaking bombes, and Colossus, among the first electronic computers, was built for it by Post Office engineer Tommy Flowers. It was renamed GCHQ in 1946.
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