Bletchley Park in Milton Keynes was the destination for our C4I Force Development trip. Home of the code breakers of the Second World War. It is now run by a charity called Bletchley Park Trust and is used as a heritage and education site.

We arrived at Bletchley Park and were met by a tour guide who directed us to Hut 4 for a coffee. Hut 4 was originally used for Naval Intelligence, but has since been refurbished as a coffee shop and restaurant for visitors of the park.

After finishing our drinks we moved on to Hut 12 and received a brief which formed the introduction to the tour. Bletchley’s local railway station had links with Oxford and Cambridge, whose universities were ideal recruiting grounds for code breakers. This made the site an ideal location for code breaking.

We received a brief on code breaking and the workings of the Enigma machine, which is a German device for encrypting and decrypting secret messages. It was these secret messages that were analysed by the residents of Bletchley Park.

The main tour started at the front of the mansion itself, which originally housed all of the code breakers. The ground floor housed the Naval, Military and Air sections, while MI6 worked upstairs. As the number of personnel grew, the code breakers had to expand beyond the mansion, and various huts were built in the grounds surrounding the mansion.

The tour guide drew our attention to the water tower at the top of the mansion. Originally, German messages were intercepted by a wireless room in the water tower. This radio station was later removed to avoid drawing attention to the site. Various other listening stations were set up around the country, and coded messages were delivered to Bletchley Park by courier on motorcycle.

Bletchley Park was affected by enemy fire on one occasion when three bombs were dropped nearby. These bombs were intended for the railway station but one of them landed by the couriers’ entrance to the park. The bomb dislodged one end of Hut 4, which was where we had coffee earlier that morning. Workmen were able to simply winch it back into position while Naval Intelligence work continued inside.

Eventually we reached the Bletchley Park Museum, which housed the bombe. The bombe was an electromechanical device designed by Alan Turing, used to help decipher German messages. For a German message to be successfully decrypted, both sender and receiver had to set up their Enigma in the same way. The bombe was used to calculate those settings for a given communication. The bombe on display was a working version that had been rebuilt for the museum. The first bombe was originally installed in Hut 1 in 1940. More and more bombes were built and by the end of the war there were around 200. Many were used at other sites in case of a bombing raid at Bletchley Park.

In addition to the Bombe, the museum contained an array of Enigma machines. It also exhibited some of the life and works of Alan Turing, and a statue of the man himself.

Our final stop was the National Museum of Computing, located in block H. This housed the Tunny and Colossus galleries. Tunny was the British name for German Lorenz-encrypted teleprinter communications.

Lorenz encryption was thought to be unbreakable; however in 1941 a German operator sent the same message twice using the same settings. This gave code breakers the insight they needed to break the code. In 1942 the British made their own Tunny machine that produced decrypts of Lorenz-encrypted messages.

Finding the settings of the Tunny machine was a complex task due to the many possible starting positions of its 12 rotors. By 1943 a machine called the Heath Robinson machine was built to assist with this task. The operator would feed a paper tape containing cipher text into the machine which would then find the settings for that given communication. In 1944 the Heath Robinson was superseded by the Colossus machine, which was faster and more reliable. The museum contains a Tunny machine and a Colossus machine, both of which are replicas built by volunteers.

Our trip to Bletchley Park was enjoyed by all that attended. It was very informative, and was particularly relevant to us as C4I personnel as it gave us a great insight into the history of our trade.

It also gave us an insight into aspects of the war that rarely seem shown off in documentaries or history books. The guides were knowledgeable on inside stories about the private life of various “characters” known in Bletchley. This new insight into not often seen aspects of the war made the trip an experience worth having.

SAC Stoker & SAC Joynes

Photography by Cpl Pierson