Much of the essential work of the Park was carried out by staff working very long hours in wooden huts, using paper and pencil, to deduce the German codes. The infamous huts, 3, 6 and 8, now in a very neglected condition, played a key part in Britain winning the war.

As the work of the codebreakers grew, larger, brick and concrete buildings were constructed to house the overflow of information from the huts.

What machines were used?

Major Ralph Tester set up the extension of the the work being done in B Block. This formed the basis of F Block which was the breaking of Hitler's most personal high command messages. Thus the work was carried out in the Testery.

Colossus was used to find the wheel settings for the more complex ciphers which were created by the German Lorenz which was a semi automatic multi-rotor machine.

The Tunny machines used the correct wheel settings to decipher the message to give plain German Text.

Fish

German codes were given the names of fishes, hence; Jellyfish, Tunny, etc...