National Museum of Computing

Few centres of wartime activity have had as much influence on the long term development of industry as Bletchley Park, a mansion adjacent to a railway junction, 60 miles north of London and now within the boundaries of the new city of Milton Keynes.


The British Government decided to move its Code and Cypher School away from central London in 1938 and acquired the site at Bletchley Park where code breakers began operations in August 1939. A wide range of activities took place there, not all of which are yet in the public domain. The first major achievement was the development of means of deciphering the German Enigma code, on which British experts were able to build on the work of Polish mathematicians who had acquired an enigma machine. Alan Turing (1912-54) and Gordon Welchman (1906-85) developed an electro-mechanical machine called the Bombe, which could find settings for the Enigma machine. Intelligence obtained through Bombe contributed substantially to Allied wartime successes. About 200 Bombe machines were built but all were broken up after 1945.


After 1945 the Bletchley Park estate remained in government ownership but was used for varied training activities, for teachers, post office engineers and air traffic controllers. Its wartime significance emerged only gradually from the 1970s, necessitating the re-writing of much of the military history of the war. In 1991 the Bletchley Archaeological and Historical Society organised an event bringing together veteran code breakers who had worked at Bletchley Park. It was quickly evident that many people were in favour of conserving the buildings and interpreting the significance of what had happened there between 1939 and 1945. The Bletchley Park Trust was formed in 1992 and in 1999 obtained a long lease of the premises. The site, where displays now include a replica of one of Turing’s Bombe machines as well as several Enigma machines, was open on a daily basis from 2004, and has since received substantial funding from English Heritage, Milton Keynes Council and the Heritage Lottery Fund.


The National Museum of Computing, which opened at Bletchley Park in 2009 is the operating name of a separate charitable foundation, the Codes & Cyphers Heritage Trust. Its outstanding exhibit is a functional replica of the Colossus computer, completed in 2007. Colossus was developed to break the codes transmitted from the Lorenz (or Tunny) machine, otherwise the Geheimschreiber or secret writer, used by the Third Reich to carry communications from Adolf Hitler and his staff to the principal German command centres throughout Europe. These codes were first broken in 1941 by the experienced cryptographer John Tiltman (1894-1982) using hand methods, but they subsequently became more complex and increased calculating power was needed to decipher them. Dr Max Newman (1897-1984) was head of the section that began to develop a suitable machine, but the task was achieved by Colossus which was designed by Tommy Flowers (1905-1998) and built at the Post Office Research Department at Dollis Hill, London, where Flowers had been employed before the war. The first Colossus machine was installed at Bletchley Park in December 1943, the second on 1 June 1944, and eventually there were 10 at the establishment. After the war it is understood that two were transferred to GCHQ (Government Communications Head Quarters) at Cheltenham and the remainder were broken up. The development of Colossus, along with other wartime activities at Bletchley Park, was kept secret until the 1970s. It is now accepted that Colossus was the first electronic digital computer that was in any sense programmable. It was a very large machine dependent for its operation on thousands of thermionic valves.  The National Museum of Computing also has displays illustrating the development of computers from Colossus to the present.


National Museum of Computing
Block H
Bletchley Park
MK3 6EB Milton Keynes
United Kingdom
+44 (0) 1908 - 374708