The Road to Colossus

It is a little-known fact that one of the most significant contributions to the Allied effort in the Second World War was made, not by a soldier, but by a computer, Colossus. According to German historians, intelligence gained from the codes that were cracked by Colossus shortened the war by two years, thereby saving the thousands of lives on both sides and averting the possibility of nuclear war in Europe.

However, if you were to look at it, this machine would bear scant resemblance to the modern personal computer, of which it was an important fore-runner. Standing 8ft high, 3ft deep and 16ft long, you could hardly transport it in a truck, let alone a briefcase.

Yet this machine, built by Post Office engineers in 1943 to decode messages that had been enciphered using the Lorenz machine, could be considered Britain's most important technological achievement of the twentieth century, anticipating developments such as parallel processing by a quarter of a century.

By the time of D-Day there were actually ten Colossi in operation, all working to establish such important information as the fact that the Germans were unprepared for the assault on Normandy, and that panzer divisions were being held in reserve in Belgium rather than being sent to counter the Allied forces.

The Lorenz machine, which was used by the Germans to scramble messages between members of the Nazi High Command, enabled a much more sophisticated level of encryption than that being used by the British armed forces. As a result, the Germans believed it to be unbreakable:

"As an example of their blind faith in the Lorenz, not only did they allow Hitler to speak directly to his generals using this machine, but on two occasions they actually sent out the cipher-setting sheets for the next month on the Lorenz machine itself,"

For the past five years Sale has been involved in a remarkable project to recreate the original Colossus to display at Bletchley Park, the home of British wartime intelligence, alongside the world's sole surviving Lorenz machine. Initially he met a wall of silence: even after 45 years, former workers at Bletchley Park were still bound to the Official Secrets Act. However, in 1993 he received special security clearance to rebuild Colossus and was permitted to interview former employees.

It turns out that the 'need to know' policy at Bletchley Park meant that none of these people knew what people in the next room were doing. (Indeed, the engineer who designed Colossus, Tommy Flowers, was led to believe for a long time that he was working on an entirely different project!)

However, in a remarkable display of perseverance, Sale was able to persuade 2,000 of these workers to submit written accounts of their work, enabling him to gain a unique insight into the intelligence network at Bletchley Park. Which the general public can now share at his code-breakers' museum.

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