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Ordnance survey map of HUT 8 AT BLETCHLEY PARK
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Statutory Address:

The building or site itself may lie within the boundary of more than one authority.

Milton Keynes (Unitary Authority)
West Bletchley
National Grid Reference:
SP 86469 33944


721/0/10021 BLETCHLEY PARK 28-SEP-05 Hut 8 at Bletchley Park

GV II BUILDING: Wooden hut, c.120m north-east of Mansion.

DATE: January 1940

ARCHITECT: Ministry of Works for Government Code and Cipher School.

MATERIALS: Brick sleeper walls supporting a timber frame clad with painted boarding, possibly asbestos. It has a felt pitched roof.

EXTERIOR: Hut 8 is a rectangular, single-storey building eleven bays (155 feet) long, aligned north-south, parallel with and east of Hut 1. Timber casement windows, some of them later C20 replacements. There is a doorway to either gable end (both with modern doors) plus two on the west side and one on the east.

INTERIORS: Internally, it is known that considerable alterations were made during the war. The Big Room, where traffic was subject to initial analysis and deciphering, is substantially intact (a subdivision introduced during the war [see below] has been removed), while to its south-east part of Alan Turing's two-bay office survives. Surviving wartime fittings include five doors and radiators.

SUBSIDIARY FEATURES: Hut 8 retains stretches of its surrounding red brick blast wall at the north end of the east wall and surrounding the south-west corner. The latter, at over 2m high, is the best survival of such a wall on site. There is a wartime lean-to against the west side of the south-west corner, and a wartime bicycle shelter to the south of the south-west corner.

HISTORY: In 1939 Bletchley Park became a dispersal home to the Foreign Office's Government Code and Cipher School. It became the focal point of inter-service intelligence activities, the place where German codes (notably those encrypted using the Enigma machine) were deciphered, the significance of decrypts assessed, and intelligence passed to appropriate ministries and commands. Bletchley Park has become celebrated for its contribution to the Allied victory, as well as for its contribution to the development of information technology. As the organisation enlarged new buildings had to be provided, firstly wooden huts and, from 1942, more permanent brick blocks.

Hut 8, constructed some time late in 1939, was occupied by the section of the name from early 1940 until February 1943. It was responsible for decoding Naval Enigma traffic - the most difficult to break - including U-boat ciphers. It was headed first by the famous mathematician Alan Turing (1940-Nov 1942), next by the former British chess champion Hugh Alexander (to December 1944), and then by A.P. Mahon. Its senior staff peaked at 16 at the end of 1941, falling to four by March 1944. At the heart of the hut was the `Big Room' which occupied the north end of the hut where intercept traffic was prepared for the `Banburists', the mathematicians who began the process of analysis which reduced the number of code variables which had to be tested for. Also carried on in the Big Room was testing of results generated by bombes (the purpose-built electromagnetic machines which were used to break the daily Enigma keys), the decoding of traffic, and routine clerical work. The decrypts of the German Enigma traffic were sent to the Naval Section (Hut 4) and thence, as Z material, to the Admiralty.

In early 1943 the section moved to Block D. The hut was renamed Hut 18 and occupied by ISOS which dealt with Abwehr (German Secret Service) Enigma traffic, followed by Naval Section V Training School. It was converted to an intercept station for `Operation Overlord', the Allied invasion of Normandy in June 1944. Finally, in July 1945, the hut was taken over by those delegated to write the wartime history of Bletchley Park. In 1978 it became a GCHQ canteen.

SUMMARY OF IMPORTANCE: Hut 8's significance is primarily historic. From the start of 1940, soon after GCCS was set up at Bletchley Park, the hut was an important component of the operation, which is renowned for its part in this breaking of the German Enigma code, and in contributing to the Allied victory (especially in the Battle of the Atlantic). Hut 8 was where German Naval Enigma traffic was decrypted, and during the period when it was headed by Alan Turing perhaps best captures the modern public perception of wartime Bletchley's character. With Huts 1 and 3 it forms part of a notable group of functionally inter-related huts representing the first phase of Bletchley Park's expansion, and externally while unprepossessing its wartime appearance is largely unaltered.

SOURCES: English Heritage, Bletchley Park (Architectural Investigations Reports and Papers B/010/2004), vol. 1, 26-38, 266-73; Feilden & Mawson, Bletchley Park Conservation Management Plan (draft 05, December 2004)


The contents of this record have been generated from a legacy data system.

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This building is listed under the Planning (Listed Buildings and Conservation Areas) Act 1990 as amended for its special architectural or historic interest.

End of official listing

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