In the summer of 1939, a small team of codebreakers arrived at the Government Code and Cipher School's (GC&CS) new home at Bletchley Park, Buckinghamshire. Their mission was to crack the backbone of German military and intelligence communications which would provide the Allies with vital information towards their war effort.

Bletchley Park was a county house situated 50 miles North-West of London, the site played host to a diverse group of code breakers, including Alan Turing and Dilly Knox. Among the ciphers that were broken were Enigma and Lorenz.

The code breakers devised methods to allow them to successfully read enemy codes, often within a few hours of the messages being received by the outlying Y-stations. New technology was invented to help with the deciphering of messages. The world’s first semi-programmable computer, known as Colossus, was invented at Bletchley Park to help with the decoding of Lorenz ciphers, which were used by the German High Command to send their most highly-classified and important communications.

It is estimated that over 10,000 people worked at Bletchley Park at the height of its wartime activity. Their work affected the fate of nations and helped shorten the war by at least two years. By March 1946, the people were gone and all evidence of their code breaking activity had been removed from Bletchley Park.