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Bletchley Park – decoding British secret history

14th March 2017



Today we visited Bletchley Park, home of the codebreakers of the Second World War. Located within the modern town of Milton Keynes, this centre played a major part in WWII history.

If you’ve watched The Imitation Game, where Benedict Cumberbatch acts the part of Alan Turing, you know what this is. We didn’t see nice old Ben but what we did see was far more interesting and oddly peaceful.



Historians believe that the activities at Bletchley Park shortened the war by as much as two years. Here, a different kind of war was being fought, a secret war. Men and women raced against time to break ‘unbreakable’ enemy codes and turn the tide in the Allies’ favour.

This group of men and women was carefully selected and brought to Bletchley Park in 1939, at the outbreak of the war.  Their work couldn’t be spoken of for many years but it often yielded results that influenced the results of the war.

“Anybody admitted at Bletchley Park during the war was allowed into a most enormous secret…”

The staff explained to us that this section of the Military Intelligence moved in after the Leon family sold Bletchley Park and the mansion. Bletchley was a strategic point, 50 miles from London, close to transports and communications links. The Oxford-Cambridge line (Varsity Line) passed through the nearby train station, and that’s where most of the codebreakers were expected to come from.



These men and women could work for 30 hours to decipher vital information heard on the wireless network. The Germans used a device called Enigma to encypher their messages before transmitting them via radio. This machine had 158,900,000,000,000,000,000 configurations. Every intercepted message would seem to be utter gibberish, unless you had the key.

The Germans were changing the key every 24 hours, by hand it was taking two weeks to break a key. How to crack this phenomenal machine? The weak point of the Enigma was that no letter could ever be encrypted as itself. For example A would never encrypt as A. The weak point of the German military was their use of predictable messages, such as the weather forecast.

Today the huts and blocks of Bletchley host an ensemble of fascinating exhibitions. We arrived too late to visit all of them, so we headed straight to Block B (after a whistlestop at the visitor centre) and ended our visit at the mansion.



Entering the museum in Block B is a jump into a past of secrecy and discovery. The centrepiece of this exhibition is the Bombe, or a fully operational rebuild of it. In 1939 Alan Turing designed this electro-mechanical device. He worked with Gordon Welchman to improve an original concept of the Polish Cipher Bureau.

The Bombe was part of the solution to decipher the Enigma encrypted code. This machine would run 24 hours a day and use a systematic search to find the settings of the Enigma machine that had encrypted the message. The German codes could be cracked even before the German recipients would read it.

The exhibition offers also a panorama of what life was like at Bletchley park during the war. Interestingly enough the mansion was dedicated to office space and not to balls and parties. Although there was no lack of entertainment during the war, it had to be sought further afield.






Bletchley Park employed 10,000 people at its heights, of which 3,000 were Women’s Royal Naval Service. At the end of the war they slowly returned to their homes. Bletchley and their work remained a well-kept secret until 1974.

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