The 'Colossus' computer at Bletchley Park, c 1943.
© Bletchley Park Trust / Science & Society Picture Library
This shows the circuitry and pulley-wheel system of the Colossus computer at Bletchley Park in Buckinghamshire. Bletchley Park was the British forces' intelligence centre during WWII, and is where cryptographers deciphered top-secret military communiques between Hitler and his armed forces. The communiques were encrypted in the Lorenz code which the Germans considered unbreakable, but the codebreakers at Bletchley cracked the code with the help of Colossus, and so aided the Allies victory.