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Ordnance survey map of HUT 11 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 86423 33987


721/0/10023 BLETCHLEY PARK 28-SEP-05 Hut 11 at Bletchley Park

GV II BUILDING: Brick hut standing north of the Mansion.

DATE: Planned late 1940, completed March 1941.

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

MATERIALS: Brick building with a slightly cambered concrete slab roof. It may have been constructed to be blast proof, as its walls are at least 500mm thick and its roof 480mm, the latter being supported on an axial steel beam.

PLAN: Rectangular.

EXTERIOR: Squat, single-storey building, close to and south of the east end of Hut 10. There doors in both east and west gables, although the latter may not be of wartime date. The east doorway is wide - possibly to allow the bulky bombe machines which it housed to be brought in and out - and has a porch (probably added in 1943). Small rectangular vents high in the walls perhaps relate to fans installed inside Hut 11 in December 1941 to counteract the considerable heat generated by the electro-magnetic bombes. Metal-framed three-light windows.

INTERIORS: Internally the hut is divided into three rooms by plasterboard and stud partitions which post-date 1943. Before this, when it was used by the Bombe Section, the hut was probably a single open space, although a supervisor's room may have been partitioned off.

SUBSIDIARY FEATURES: Adjacent to the east door is a lean-to bicycle shelter, probably of 1943, with brick side walls and an asbestos roof.

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.

The Hut 11 complex, comprising Huts 11, 11A, and 11B (demolished after the war), housed the Bombe Section, superseding Hut 1 which was timber-framed and cramped. Bombes were electro-magnetic devices, developed from an original idea conceived by the Poles (who called their machine `Bomba', probably because it had weights which dropped - like bombs - when correct wheel settings were identified) in the late 1930s and developed into a more sophisticated form in 1939 by Gordon Welchman, Alan Turing, and Harold Keen. Bombes were an automated means of testing hypotheses (called menus) for the daily setting of an Enigma machine by working through the 150 million million settings its rotors, rings, and plugsettings were capable of. By November 1939 the first bombe machine had been ordered from the British Tabulating Machine Co. of Letchworth, and this was delivered to Hut 1 in March 1940.

The first of the three huts, 11, was planned in late 1940 and completed in March 1941. Designed to protect the bombe machines - of which there were apparently nine when first fitted out - from blast, it was the first brick-built structure on site. It superseded Hut 1, the original home of the Bombe Section, which was timber-framed and crowded. After Hut 11A was constructed in February 1942 the bombe machines were moved out and thereafter Hut 11 was mainly used for training bombe operators. Later in the war, when the much larger number of bombe machines was housed on outstations elsewhere, Hut 11 served as a store for the WRNS.

In 1945 the Hut 11 complex was handed over to MOW direct labour organisation which used it as carpenters' workshops and stores. When the Bletchley Park Trust was formed in 1992 Hut 11 was refurbished to house a display about the history of the bombe.

SUMMARY OF IMPORTANCE: Hut 11's importance is principally historical. Bletchley Park 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). The Bombe Section in the Hut 11 complex was an essential component of the code-breaking network, human and mechnical. The bombes were moved to the purpose-built Hut 11 from the vulnerable wooden Hut 1 in March 1941, Hut 11 being the first wartime brick building at Bletchley Park. Hut 11A, which largely superseded it, stands alongside. Hut 11 is a relatively small, and certainly undistinguished building architecturally, but is externally much as when built while internally it retains the open space provided for the installation of the bombe machines. This recommendation is informed by considerable English Heritage research, cited below.

SOURCES: English Heritage, Bletchley Park (Architectural Investigations Reports and Papers B/010/2004), vol. 1, 26-38, 292-308; 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.

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