H Block at Bletchley Park

Bletchley Park, Sherwood Drive, Bletchley, Milton Keynes, MK3 6EB

Listed on the National Heritage List for England. Search over 400,000 listed places

Overview

Heritage Category:: Listed Building
Grade:: II
List Entry Number:: 1391162
Date first listed:: 17-Dec-2004
List Entry Name:: H Block at Bletchley Park
Statutory Address:: Bletchley Park, Sherwood Drive, Bletchley, Milton Keynes, MK3 6EB

The Missing Pieces Project

Share your view of unique places.

Add your contribution

Location

Location of this list entry and nearby places that are also listed. Use our map search to find more listed places.

There is a problem

Use of this mapping is subject to terms and conditions.

This map is for quick reference purposes only and may not be to scale.

What is the National Heritage List for England?

The National Heritage List for England is a unique register of our country's most significant historic buildings and sites. The places on the list are protected by law and most are not open to the public.

The list includes:

🏠 Buildings
🏰 Scheduled monuments
🌳 Parks and gardens
⚔️ Battlefields
⚓ Shipwrecks

Find out more about listing

Historic England Archive

Search over 1 million photographs and drawings from the 1850s to the present day using our images archive.

Find Photos

Official list entry

Heritage Category:: Listed Building
Grade:: II
List Entry Number:: 1391162
Date first listed:: 17-Dec-2004
List Entry Name:: H Block at Bletchley Park
Statutory Address 1:: Bletchley Park, Sherwood Drive, Bletchley, Milton Keynes, MK3 6EB

This List entry helps identify the building designated at this address for its special architectural or historic interest.

Unless the List entry states otherwise, it includes both the structure itself and any object or structure fixed to it (whether inside or outside) as well as any object or structure within the curtilage of the building.

For these purposes, to be included within the curtilage of the building, the object or structure must have formed part of the land since before 1st July 1948.

Understanding list entries

Corrections and minor amendments

This List entry helps identify the building designated at this address for its special architectural or historic interest.

For these purposes, to be included within the curtilage of the building, the object or structure must have formed part of the land since before 1st July 1948.

Understanding list entries

Corrections and minor amendments

Location

Statutory Address:: Bletchley Park, Sherwood Drive, Bletchley, Milton Keynes, MK3 6EB

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

District:: Milton Keynes (Unitary Authority)
Parish:: West Bletchley
National Grid Reference:: SP 86335 34057

Details

This list entry was subject to a Minor Amendment on 20/07/2020

721/0/10012

Bletchley Sherwood Drive Bletchley Park H Block at Bletchley Park

(Formerly listed as H Block at Bletchley Park) 17-DEC-04

GV II Block H. 1944. Ministry of Works and Planning, for the Government Code & Cypher school.

MATERIALS: reinforced concrete with hollow clay block walls; corrugated asbestos roof. Boiler house built of Fletton brick. Mainly timber framed windows, hung from above: some refenestration has occurred.

PLAN: inverted T-shape. Off the narrow northern spur on the west side is a lavatory annexe.

EXTERIOR: single storey. South range comprises a taller boiler house with water tower and chimney, flanked by machine rooms to east and west. These comprise pairs of Standard Huts placed alongside each other, with a valley roof above. Continuous strips of windows at upper ground floor height. Northern range, 26 bays in length.

INTERIOR: the machine rooms at the southern end have been sub-divided: they formerly had posts supporting the valley roof along the middle, creating large open spaces housing the computers. The corridor along north range survives, although dividing walls in the rooms along the east side (used in part for the initial analysis of decrypted material) have been repositioned.

HISTORY: Block H was the last significant building to be erected at Bletchley Park in WW2. Plans were approved on 25 May 1944: it was ready for occupation on 17 September 1944. It was built on the western edge of the site as an annexe to the now-demolished Block F (pulled down in 1987), which was located immediately to the east, and its purpose was to work on the decipering of the 'Fish' series of encrypted German teleprinter transmissions. The large machine rooms at the southern end were built to house six 'Colossi' (Nos 6 - 11 at Bletchley Park): this was necessary, given the volume of signals being intercepted, and the pivotal role of Bletchley Park in the overall Allied intelligence-gathering process. The Colossus computer was developed in 1943 by Tommy Flowers, based on designs by Max Newman. First housed in the southern annexe of Block F, Colossus II was accommodated in this purpose-built structure. After 1945 the building was adapted for use as a training centre for the Post Office, and the northern range was extensively altered. The building was opened as a museum in 1994, housing a replica of the Colossus.

SUMMARY OF IMPORTANCE: Block H is architecturally undistinguished, being a utility design incorporating a standard Ministry of Works 1942 hut design (see The Builder, 28 August 1942, 176). Nonetheless the building has strong claims to international historical note as being the world's earliest purpose-built building erected specifically for electric computers (Block F, now demolished, included an annexe designed to house computers but Block H was designed from the outset to serve this purpose). The Colossus is regarded as being the world's first programmable electronic digital computer: Bletchley Park witnessed the earliest mass-installation of computers, and is thus a key site in the development of information technology. It also forms part of the ensemble of surviving wartime buildings at Bletchley Park which, through their deciphering of encrypted Axis messages, made a significant contribution to Allied victory in the Second World War. The adjoining brick building to the north-east is excluded from the listing.

SOURCES

Linda Monckton et al, 'Bletchley Park' (English Heritage Historic Buildings Report B/101/2004: 4 vols 2004), esp. II, 540-49; IV, 29 & 75.

Legacy

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

Legacy System number:: 493066
Legacy System:: LBS

Sources

Books and journals
'The Builder' in 28 August, (1942), 176

Legal

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