Bletchley Park’s Colossus Rebuild

This summer, while doing research at the UK National Archives, I was fortunate enough to be able to take a side-trip to the Bletchley Park historical site in Milton Keynes.

The site of some of the most important codebreaking of World War II, Bletchley Park now functions as a museum of early British codebreaking and computing. A dedicated team there has painstakingly constructed a working model of the Colossus, the 1900-vaccuum tube behemoth designed and built by London Post Office engineer Tommy Flowers in 1943 to speed “Tunny” codebreaking operations using codebreaker William Tutte’s statistical method. The Colossus rebuild is a sight to behold–and hear–as you can see from the video below:

Though Turing and his electromechanical Bombes get a lot of credit for wartime codebreaking successes (there is a working Bombe rebuild at BP too), it was Flowers’s Colossi that sped up British codebreaking to the point of maximal utility. They were the first digital, programmable computers to harness the speed of electronics for time-sensitive, mission-critical work. His team produced 10 of the massive machines between late 1943 and the war’s end, frantically working out of a factory-like workshop in Birmingham after building the first Colossus at the Dollis Hill Research Station in London. Colossus II, installed just days before D-Day, was so critical to the success of the D-Day landings that (as B. Jack Copeland reports) the operators had to keep the machine running despite the floor being flooded–they put on thick rubber boots so that they didn’t get electrocuted.

You can see an image of Women’s Royal Naval Service members working on a Colossus here. (From I. J. Good, D. Michie, and G. Timms, General Report on Tunny With Emphasis on Statistical Methods, 1945, 332, HW 2/25, TNA). The workers have been identified as Dorothy Du Boisson (left) and Elsie Booker (right) by historian B. Jack Copeland.)

While I was at the exhibit, I overheard a father trying to explain to his young son what the Colossus was, in terms he thought the boy might understand. Brandishing his iPhone, he said: “See, this phone is millions of times more powerful than that big computer.”

Call me back when your iPhone wins a war, I thought.