A visit to Bletchley Park

In July I paid a visit to the Bletchley Park Museum.

During the war this housed the code breakers of the Government Code and Cypher School (GC&CS) which after the war became GCHQ.

This was the place where the boffins who cracked the Enigma and Lorenz codes and other codes and cyphers worked in conditions of great secrecy.  It also was home to scores of mainly female workers who ran the bombes that analysed the settings of Enigma, as well as translators who would convert the German messages  (and other languages) into English, intelligence officers who would interpret the reports and many other specialists. Their story was not told until decades after the war. Yet their work may have been the single most important action in the war – saving countless lives and shortening the war by perhaps 2 years. It was here that the location of German U-boats were determined – helping win the Battle of the Atlantic. They were able to find out the targets of bombing raids, the locations of enemy units and even the progress of the V weapons projects. Their contribution to the planning of the land campaigns in Africa, Italy and Normandy was pivotal.  This museum is a superb place to find out all about that.

Several of the Huts are available to visit. Many have the offices setup as they were during the war.

The museum occupies the very huts and Mansion the code breakers worked in. The different huts had different functions. So those working in Hut 8 (like Alan Turing) invented methods and machines to be used to analyse the settings of the code machines, Hut 11 housed the bombes that they designed, Hut 6 actually deciphered the Enigma code and Hut 3 would then take the messages which were in German and translate them into English. (The messages being pushed between the two huts, along a wooden shut by a broom handle – such are the small details of such significant activities). Hut 4 housed analysts who worked out what the messages meant and their significance.

The Mansion was the original house of the estate and the first part of the base to become operational when the government took it over.

The lake and gardens of Bletchley Park became important as the code breakers would take breaks in the grounds and in the winter skate on the frozen lake. Unable to discuss their work the workers filled their free time with pursuits like concerts, dances, chess competitions, rugby games and dozens of other activities – many of the programmes and records of which still exist in an exhibit on life at the park..

The lake which would freeze over in the winter.

There were many codes and cyphers in use but two machines in particular became the focus of much of the activity at Bletchley Park.

Enimga

Enigma was used to send generally shorter messages like weather reports and orders to U-boats. An operator could type in a message, then scramble it by using three to five notched rotors, which displayed different letters of the alphabet. This would then be transmitted over wireless by simple morse code to a receiving station. The receiver needed to know the exact settings of these rotors in order to unscramble the text. Otherwise it was just a string of meaningless letters.

These settings changed each day and with several wheels, in various orders with multiple ways of configuring each cog there were believed to be hundreds of trillions of combinations. Over the years the basic machine became more complicated as German code experts added plugs with electronic circuits. Breaking this code needed machines and humans to work together. The machines- called bombes could analyse possible settings and see if they were the right ones. Yet humans had to devise a short list of possible settings to test and that is where the genius of the code breakers came in. They would make a guess as what part of the message might be (Maybe “weather report Atlantic” )and then suggest settings that would work with that message.

One of the bombes that could test Enigma settings. This one is an working replica at the museum. All the originals were destroyed.

Lorenz was even more complicated than Enigma and was used for longer messages. It was sent by teleprinter and generated electronically. The Lorezne machines changed the text so anyone intercepting it would not understand it.

Analyzing the Lorenz machine settings required machines even more advanced than the bombes that cracked Enigma. The earliest computers, called Colossus were actually developed to work out the Lorenz setting once a break through by an accademic called Bill Tutte was made. He worked out that the pattern used to scramble the text was actually a repeating cycle. There is a replica of Colossus in the adjacent National Museum of Computing which is work seeing to get the full picture. It is fascinating to consider how much he efforts in Bletchley kickstarted the whole computer revolution.

Colossus

One of the great code breakers was of course Alan Turing who was massively involved in cracking enigma. There is a fantastic statue of him at the museum

You can also visit his office. Its amazing to be able to stand in the very place that Enigma was cracked. As with most of the offices it is pretty plain and simple. Many of the offices are created like this – often with videos of actors playing the roles of the code breakers and snippets of conversations can be heard in he rooms.

Alan Turing’s office

The National Museum of Computing on the same site (not open every day) has working originals or replicas of the early computers (including Colossus) and the chance to try out the earliest computer games and do some coding if you can remember how to do it or ever could!  If you are looking to visit allow a full day for both sites.

Find out more about Bletchley Park here.

With the family outside the mansion.