Tommy Flowers

1905 - 1998

Under war-time pressure it took just eleven months for Tommy Flowers to design and build Colossus at the Post Office Research Station, Dollis Hill, in North West London. After a functional test, Colossus Mk 1 was delivered to Bletchley Park in late December 1943, and was working by early January 1944.

Colossus was not a general purpose computer in the sense we now understand it. It was designed specially for World War 2 code breaking. But it was programmable to some extent. Colossus proved conclusively that one could build reliable systems using thousands of valves, something that had not been done before. Valves were thought to be unreliable until the Colossus engineers developed techniques to deal with this. The use to which the Colossi were put was of the highest secrecy. Colossus itself was top secret and remained so for many years after the War. Because of wartime and post-war secrecy Colossus did not feature in accounts of the history of computing for decades after the war, and the achievements of Tommy Flowers and his team were not recognised till many years later. A complete working Colossus Mark 2 has been built at the National Museum of Computing at Bletchley Park and stands in the same place as that originally occupied by Colossus 9 in Block H. Based on only scraps of diagrams, old pictures and half-forgotten memories, Tony Sale and his team re-created this remarkable world-first for Britain, and the Colossus rebuild project has led the way for other ambitious reconstruction projects that memorialise historic British computers.

It is widely held that Tommy Flowers and the codebreakers at Bletchley Park helped shorten the Second World War by several years.