Ancient Monuments

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MoD CORSHAM: GPO Telephone Exchange

A Scheduled Monument in Box, Wiltshire

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Latitude: 51.4217 / 51°25'18"N

Longitude: -2.2177 / 2°13'3"W

OS Eastings: 384956.797727

OS Northings: 169210.47368

OS Grid: ST849692

Mapcode National: GBR 1RF.XSP

Mapcode Global: VH96H.HJYG

Entry Name: MoD CORSHAM: GPO Telephone Exchange

Scheduled Date: 20 March 2013

Source: Historic England

Source ID: 1409129

County: Wiltshire

Civil Parish: Box

Built-Up Area: Corsham

Traditional County: Wiltshire

Lieutenancy Area (Ceremonial County): Wiltshire

Church of England Parish: Box

Church of England Diocese: Bristol


A series of rooms contained within the worked-out chambers of a former Bath stone quarry, adapted to an underground government facility in the mid C20: Central Government War Headquarters (CGWHQ). The rooms have been fitted to provide a telecommunications facility, including two telephone exchange operator consoles and a supervisor desk in one area, and a number of rooms to the rear with plant and racking containing the associated equipment required for a telephone exchange.

Source: Historic England


PRINCIPAL ELEMENTS: the GPO Telephone Exchange, or 'Woodlands', is divided into separate operational areas over 5419 square metres. It comprises large manual switchboards, automatic telegraph and telephone switching and comprehensive transmission facilities. These combine to form a large telecommunications facility. Sub-areas within have been separated by inserted concrete block walls, and stand on two levels.

DESCRIPTION: the principal operational area of the GPO Telephone Exchange is in Rooms 82 and 83, the Manual Switch Board Rooms, to the immediate north of East Main Road. Room 83 contains two multi-position telephone operator switchboards. 'Suite 1' has 40 positions, with 15 cord circuits each; and 'Suite 101' with 14 positions and 8 circuits each. The boards are constructed of mahogany. At the west end of the room is a directory enquiry desk with four positions, and a supervisor's desk. The desks are in a rapidly deteriorating condition. Further west, stairs lead to an upper level, Room 82. The areas to the north of this upper level (Room 81 and part of Room 68) are open with supporting columns and tiled flooring. While they form part of the Exchange facility, they have never been equipped and are not considered part of the operational area and are not included in the scheduling.
The rooms to the north of Room 83 contain metal telecommunication frames with equipment, plant rooms, engineers work stations and workshops. Room 72 is the Automatic Telephone Exchange and contains a metal frame with installed telecommunications equipment. Room 71 contains the large Main Distribution Frame (MDF), a substantial feature that is largely unfilled frame with travelling timber ladders to access the upper parts. The MDF functions as the termination point for cables in the Exchange. Further equipment in the facility includes an Automatic Telegraph Exchange in Room 68. An Engineer Test Desk, stands in the north-east corner of Room 68, with two positions.

Neighbouring areas contain the necessary plant to run the facility, including Air Compressors (Room PR2), an Air Handling Unit (Room PR1), and a Telephone Repeater Station. The TRS and TGH Power Room (Room 70) contains a motor alternator, regulatories and a standby generator that could run the whole of Woodlands. Other fixtures include light fittings showing the Exchange status, with attached bells and Public Address loudspeaker (Room 70). To the far north are store areas and the perimeter walls of the CGWHQ. Across the GPO Telephone Exchange, different areas are delineated by different coloured floor tiles.

The non-operational part of the Exchange, including extensive areas which were never fitted with equipment but were allocated for potential expansion of the facility, are excluded from the scheduling, although they represent an interesting context to the areas of higher national importance. Otherwise, the designated area extends to 1m around the designated boundary, and 1m above and below. All above ground structures are excluded from the designation.

Source: Historic England

Reasons for Scheduling

The GPO Telephone Exchange in the CGWHQ below MoD Corsham is designated as a Scheduled Monument for the following principal reasons:
* Period: the peril from the threat of nuclear strikes that Britain faced during the Cold War is inherent in the installation of this large-scale facility underground to provide telecommunications across the country following a nuclear strike.
* Rarity: this is the only known telephone exchange of its type. Some pieces of equipment, such as the Automatic Telegraph Exchange, are thought to be the only surviving examples of their type.
* Survival: the extensive equipment survives largely intact and in situ, although the PBMX consoles have developed surface damage through damp conditions and isolated incidents of roof fall.
* Group Value: the supreme importance of the CGWHQ site during the Cold War is an unparalleled example of our national military heritage during this era and furthermore represents the systematic use of underground areas for military and industrial use of expansive underground areas during the C20.
* Representative: the sober fitting out of the Bath Stone chamber, with breeze block partitions, is redolent of the grim character of the Cold War era and the functional nature of the area.

Source: Historic England


Books and journals
Catford, N, Burlington, (2012)
Hennessy, P, The Secret State, (2010)
McCamley, N J, Cold War Secret Nuclear Bunkers, (2002)
McCamley, N J, Secret Underground Cities, (2000)
McCamley, N J, Second World War Secret Bunkers, (2010)
Fox, S, 'Subterranea' in Top Secret - Acid, (2010)

Source: Historic England

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