Colossus computer

Colossus was the world’s first digital electronic computer. Designed by Tommy Flowers (1905-98) at the Post Office Research Station in Dollis Hill, it was taken to Bletchley Park, Buckinghamshire, site of the UK’s main decryption establishment. Here it tackled its first coded German messages in 1943.

The machine was used to crack the German Lorentz cipher, a code much harder to decrypt than the one used by the Enigma machine. But even with these impressive capabilities, Colossus had to be rapidly upgraded. A new version was commissioned just five days before the D-day landings in June 1944.

By the end of the Second World War, no fewer than ten Colossus machines were working at Bletchley Park. The importance of Colossus was not recognised for many years, as all those who worked on it were sworn to secrecy and all the machines were destroyed at the end of the war. It is now recognised as the world’s first electronic digital fixed-program computer.