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Bletchley Park
World War II codebreaking centre

Bletchley Park, commonly abbreviated BP, is an estate in the town of Bletchley, Milton Keynes (UK). During WWII, it was the UK's main codebreaking centre. The codes and ciphers of many countries were broken here, such as traffic from the German Enigma, the Siemens T-52 Geheim­schreiber and the Lorenz SZ-40/42. It's the place where brilliant people like Dylwyn Knox, Alan Turing, Gordon Welchman, and about 12,000 others helped shortening the war by several years [1].

BP is now a museum that is open to the public every day. If you are interested in the history of code and ciphers, BP is well worth a real-life visit. Many war-time buildings, such as the mansion, the cottage, the stableyard, H-Block, B-Block and some huts are still in existence.

The image on the right shows the Mansion, which is one of the most prominent buildings on the site. But there is much more to see. BP has an interesting collection of cipher machines, such as Enigma, Lorenz SZ40/42, Siemens T-52 Geheimschreiber and much, much more.

Furthermore, the on-site National Museum of Computing 1 (TNMOC), is home to Colossus, Heath Robinson and the Bombe — the machines that were used during the war to break the Enigma and Lorenz cipher machines of Nazi-Germany. They are operational and are demonstrated regularly.

 History of Bletchley Park

  1. TNMOC is an independent trust with its own admission fee and a separate entrance.

The Mansion at Bletchley Park
The Mansion at Bletchley Park
The Cottage at Bletchley Park where Alan Turing worked in isolation on solving the Naval Enigma
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The Mansion at Bletchley Park
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The Mansion at Bletchley Park
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The Cottage at Bletchley Park where Alan Turing worked in isolation on solving the Naval Enigma

Bletchley Park today
The map below gives a good impression of the situation at Blechley Park today. Most of the war­time buildings and huts are open to the public and are home to interesting exhibitions related to code­breaking. Note that The National Museum of Computing (TNMOC) — located in the top left corner and well worth a visit — is at the same site, but has its own entrance and admission fee.

Map of Bletchley Park

In the years following WWII, the layout of the Bletchley Park site has changed somewhat. Furthermore, part of the grounds of been sold for housing development, and the location of the main entrance was moved from Wilton Avenue to Sherwood Drive, accross the street from the Bletchley railway station. The map above shows the layout of the Bletchley Park site in 2012. Click the map for a closer look, or download it as a PDF here.
Enigma Display
Block B at Bletchley Park houses one of the most impressive collections of Enigma machines in the world. The image on the right shows the gallery that was opened in 2009. It allows the public to view a variety of Enigma models from all sides.

There is a standard 3-wheel Enigma I, a Naval M4, the famous G-312 Abwehr Enigma, the commercial Enigma K, the rare Enigma T (that was built for the Japanese) and some special machines that were modified at BP during WWII.

 More about Enigma


Bombe rebuild project
During WWII, British codebreakers Alan Turing and Gordon Welchman developed a mechanical machine – known as the Bombe – that was used for breaking messages created on the well-known German Enigma cipher machine.

As none of the original Bombe machines has survived, a team led by John Harper has built a fully operational replica which was completed in 2007. The machine is now located at TNMOC and is demonstrated regularly.

 More about the Bombe


TUNNY Gallery
During WWII, the Germans used the high-end Lorenz SZ-40/42 cipher machine for messages at the highest level of OKW — the German High Command. The codebreakers named it TUNNY.

Heath Robinson was the first machine that was built to help breaking the Lorenz cipher. It was developed by GPO Engineers Tommy Flowers and Frank Morell. In 2001, Tony Sale built a working replica of this machine, which is now on display at the computer museum (TNMOC) in Block H.

 About Heath Robinson


Colossus rebuild project
As the Heath Robonson machine had several problems and limitations, GPO engineer Tommy Flowers developed and built Colossus, the first programmable electronic computer.

After the war, all Colossi were destroyed or dismantled. In 1991, a team led by Tony Sale started rebuilding Colossus, using more than 1750 valves. It is now fully operational and on permanent display at TNMOC.

 More about Colossus


The National Museum of Computing

Probably one of the largest collections of computers in the world, is on display in H-Block — one of the former war-time buildings. The museum shows the full history of computing and many of the machines can actually be operated. You will certainly recognise some old friends here. Note that TNMOC is a separate entity that is not linked to the Bletchley Park Trust in any way. It is also the home to the Colossus Rebuild, the Bombe Rebuild and the Heath Robinson Rebuild.

 More about TNMOC

The Enigma gallery at Bletchley Park. Click for a larger view.
Working Bombe replica at Bletchley Park Museum
The Heath Robinson rebuild at TNMOC
The Colossus Rebuild at TNMOC
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The Enigma gallery at Bletchley Park. Click for a larger view.
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Working Bombe replica at Bletchley Park Museum
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The Heath Robinson rebuild at TNMOC
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The Colossus Rebuild at TNMOC

The name Bletchley Park dates back to 1877, when Samuel Lipscomb Seckham purchased the estate and built a farm house. Six years later, on 4 June 1883, it was bought by Sir Herbert Samuel Leon (1850-1926) who was a financier and Liberal MP. He expanded Seckham's farm house with a mixture of architectural styles into what is now known as The Mansion [1].

The image on the right shows the mansion around 1908. It was taken from a Kingsway Real Photo postcard that was date-stamped 8 DEC 1908, which means that the photograph must be older than that. At that time, the estate was still owned by Sir Herbert Leon and his wife Fanny.

After Fanny died in 1937, the site was sold in 1938 to a builder, and plans were made for demolition of the mansion. However, before the site with its typical mansion was destroyed, it was bought by Admiral Sir Hugh Sinclair, then Director of Naval Intelligence and head of MI6.

Bletchley Park was considered a convenient location, as it was within walking distance from the Bletchley railway station, right at the junction of the railway lines between Oxford and Cambridge (the Varsity Line) and the line from London to the north. As we now know, the universities of Oxford and Cambridge would supply a significant number of code-breakers during the war.

In order to disguise the true identity of the park, the first government visitors were announced as Captain Ridley's shooting party. The Government Code and Cypher School (GC&CS) officially moved to Bletchley Park (BP) on 15 August 1939, when the first wave of code-breakers arrived. The rest is history. During the war, some 12,000 people worked at BP, 80% of whom were women. They were sworn to secrecy and it wasn't until Admiral Frederick Wintherbotham's book The Ultra Secret came out in 1974, that some of them started talking about their war-time work at BP.

After the war, the park had various owners and remained in use for several purposes. It was used, for example, by the General Post Office (GPO), later British Telecom (BT), Property Advisors to the Civil Estate (PACE) and the Government Communications Headquarters (GCHQ), the post-war successor to GC&CS). The latter closed its training facilities at Bletchley Park in 1987.

By 1991 the estate was largely abandonned and plans were afoot for demolition of all buildings. On 10 February 1992 however, most of the park was declared a conservation area by the the Milton Keynes Borough Council. Three days later the Bletchley Park Trust was established, with the intention to turn the estate into a museum. This was largely the result of an active campaign by Tony Sale and a group of interested people. Finally, in 1993, the museum opened to visitors.

Initially the museum was open to the public every other weekend and the facilities at the park were limited. There was virtually no carpet and the roofs of some of the huts were leaking. But it told the fascinating story of the codebreakers extremely well. Today, Bletchley Park is turned into a modern attactive museum with all facilities that you can think of. And it is open every day.

Former exhibitions
In the past, BP hosted a variety of other museums and collections, including the Churchill Collection, the Diplomatic Wireless Service (DWS), the Milton Keynes Model Railway Society, the Toys and Memorabilia Collection and the re-enactment group 65th Nachrichten Abteilung.

Following a series of reorganisations at the museum, and refurbishment of several wartime huts, these collections have been discontinued, whilst the huts have become part of the Bletchley Park Museum. Visit the Bletchley Park website for the latest information. Below is a list of former exhibitions, all of which are discontinued.

  • Diplomatic Wireless Service (Hut 1)
  • Bletchley Park Post Office
  • Bletchley Park Garage
  • The Churchill Collection
  • Home Front Display (part of B-Block exhibition)
  • Maritime Display
  • Light Infantry at Pegasus Bridge
  • Pigeons at War
  • The Projected Picture Trust
  • The Toys and Memorabilia Collection
  • 65th Nachrichten Abteilung
  • Milton Keynes Amateur Radio Society
  • Milton Keynes Model Railway Society
Past events
  1. Detailed map of Bletchley Park
  1. Wikipedia, Bletchley Park
    Retrieved March 2008.

  2. Tony Sale, Code and Ciphers
    Website by the first curator of Bletchley Park.

  3. John Harper, The Bombe Rebuild Project
    Website, showing the progress and the various stages of the project.
Further information
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Crypto Museum. Created: Tuesday 14 July 2009. Last changed: Monday, 22 January 2024 - 14:10 CET.
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