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Former 10 Group Royal Observer Corps Headquarters, Poltimore Park

A Grade II Listed Building in Poltimore, Devon

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Latitude: 50.7545 / 50°45'16"N

Longitude: -3.4589 / 3°27'31"W

OS Eastings: 297186

OS Northings: 96006

OS Grid: SX971960

Mapcode National: GBR P2.YTMY

Mapcode Global: FRA 37N2.SCD

Entry Name: Former 10 Group Royal Observer Corps Headquarters, Poltimore Park

Listing Date: 8 April 2013

Grade: II

Source: Historic England

Source ID: 1411752

Location: Poltimore, East Devon, Devon, EX1

County: Devon

District: East Devon

Civil Parish: Poltimore

Traditional County: Devon

Lieutenancy Area (Ceremonial County): Devon

Church of England Parish: Poltimore with Huxham

Church of England Diocese: Exeter

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A Royal Observer Corps (ROC) Group Headquarters or ‘control’ building of 1960-1 built for the Home Office to a design drawn up by the Ministry of Public Buildings and Works.


A ROC Group Headquarters or ‘control’ building of 1961-2 built for the Home Office to a design drawn up by the Ministry of Public Works, under the supervision of E.C. Godwin, Chief Superintendent for Drawings.

MATERIALS: it is built of rendered reinforced brickwork with a flat reinforced concrete roof, fitted with steel blast doors and baffles.

PLAN: the building has a sub-rectangular plan with an off-centre axial corridor that originally served accommodation rooms, offices, ablutions and latrines to its south-west, and operations, GPO, plant, and canteen rooms on its north-eastern side.

EXTERIOR: it is a single-storey, rendered reinforced structure, spanned by a central square-plan upper-storey, raised above the level of the flat asphalt covered reinforced concrete roof. The roof is hidden behind a low parapet wall with flat concrete slab coping stones. Drain openings in the parapet permit rainwater to pass through the wall to be gathered in painted rectangular storm boxes and metal rainwater goods attached to the walls. The structure is devoid of any decoration apart from a stepped brick door surround and projecting brick piers on the corners of the main south-east elevation. The entrance is recessed to form a blast baffle and there are two steel blast doors at right angles to the main entrance. The door on the northern side allowed access to the particulate filter room, and the southern door allowed access into the main structure via an air-lock porch. A similar recessed doorway with a single steel blast door in the southern wall exists in the centre of the north-west elevation and served as an emergency exit.

Two ventilation flues and a cooling tower are built against the south-east elevation of the raised central upper storey. A triangular galvanised steel telescopic lattice radio mast is situated against the south-west wall of the building. The walls have no fenestration; the only openings being for ventilation intakes and exhausts, all of which are protected by steel plates, and those on the cooling tower have projecting galvanised steel cowls. Associated monitoring equipment, such as the sensor head of a remote nuclear explosion sensing device called - Atomic Weapon Detection Recognition and Estimation of Yield (AWDREY), have been removed from the roof of the cooling tower and the roof over the triangulation alcove of the operations room, although mountings remain.

The face of the north-east elevation breaks forward towards the southern end where the stand-by generator and plant room are housed and an exhaust pipe from the diesel engine is attached to the wall. The rendered surface of the building was originally painted white to reflect the heat generated by a nuclear explosion. Since 2006, the north-east and south-east elevations have been re-painted olive green, in addition the plinth, door surround, brick piers and coping stones have also been painted black.

INTERIOR: the Group HQ is entered from the blast baffle in the south-east elevation via a steel blast door that leads into an air-lock at one end of the off-centre axial corridor. The corridor is flanked on one side by the stand-by generator, the air conditioning plant, the GPO equipment rooms, the operations room, kitchen and the canteen. On the other side, it is flanked by the former domestic rooms including the decontamination rooms, latrines, dormitories and the officers’ room. A stairway rises to the upper floor which contains an emergency water tank, wireless room, and operations room gallery. The building was de-stored at the time of the stand-down of the ROC, but retains a number of historic fittings and fixtures. An empty battery charging cabinet associated with the AWDREY equipment remains in the wireless room. The timber desk for the plotters, tellers, and supervising officers form a parapet around the three sides of the gallery. Rotating Perspex covered post plotting boards are attached to the desk on the northern side of the gallery, and a triangulation table with associated bomb tote boards is situated in the triangulation alcove in the northern corner. A timber partition wall clad with sound deadening panels on the ground floor of the operations room defines the former teleprinter room. In the northern corner of the operations room is the dose-rate alcove, which retains its chart display board. A number of openings have been cut through the walls in the early C21 and relate to the building’s current use.

SUBSIDIARY FEATURES: associated with the Group HQ are two small detached structures; a diesel oil tank and an isotope store. The former is situated near the north-eastern corner of the Group HQ covered by a low rectangular and slightly domed concrete roof. The isotope store is situated near the north-west corner, and was used for storing tins containing low-level radio-active sources for calibrating the fixed survey meters. It is a rectangular, single-storey, rendered brick structure with a projecting flat, reinforced concrete roof. The interior is protected by a baffle wall and is entered by an offset doorway. Bricks have been cut out in each elevation to give the store the appearance of a pillbox and an open timber observation post has been built on the roof; all of these features are secondary and associated with its current use.


The Royal Observer Corps can trace its history back to the First World War when a system of aircraft reporting was developed by Major General E B Ashmore in the London Air Defence Area, making use of telephone reporting to enable centralised aircraft movement plotting using a standardised gridded map system. This organisation was stood-down at the end of the First World War, but approval was given to re-constitute it in 1924 and the Observer Corps was officially inaugurated in October 1925. Over the subsequent years the Corps gradually extended its area of operations across the whole of the United Kingdom, with No.21 Group being formed in Exeter in 1940 with the group headquarters ‘control’ being installed over the General Post Office in the High Street, Exeter. Royal recognition of the Corps’ services was given in April 1941 when King George VI bestowed the ‘Royal’ prefix to the Corps’ title, becoming the Royal Observer Corps (ROC).

During the early hours of 4 May 1942, Exeter was subjected to an intense bombing raid, part of the so-called ‘Baedeker Blitz’ mounted against historic city centres. Despite heroic efforts being made by the firewatchers and the National Fire Service, fires quickly took hold; particularly around the High Street, where the ROC had to abandon their Group HQ. As a result the Group temporarily moved to an ‘emergency centre’ situated at The Quay while a new headquarters was being prepared at Barnfield, Southernhay, Exeter, where it stayed until the ‘Stand-down’ in 1945. The ROC was re-constituted in 1947 as part of the response to the growing international tensions that developed into the Cold War. Since the former Group HQ building at Barnfield had passed into private ownership, the Group HQ was set up at the Ground Control Interception radar station at RAF Exminster, but then moved to the former No.10 Group Fighter Command Sector Operations Block at RAF Poltimore Park, where it remained until 1961.

The Group was re-designated No.10 Group in 1953 and the ROC’s role of aircraft reporting was changed to one of to nuclear monitoring in June 1954. In general, the ROC was ill-prepared for the new role, as the old observation posts and group controls offered no protection from the effects of a nuclear explosion; however, eventually the Ministry of Public Buildings and Works produced designs for underground nuclear monitoring posts and two designs of ROC Group HQ - a semi-sunken design covered with earth for areas at high-risk of attack and one on the surface where the risk of attack was perceived as being low.

The nuclear reporting and monitoring role was formalised in 1957 and the ROC became a major component of the United Kingdom War Monitoring Organisation (UKWMO). In 1961 a new semi-protected Exeter ROC HQ was completed adjacent to the former RAF sector operations block; the latter being then used by the ROC as an administration building and all operations were moved to the new building. The Group HQ was manned by about seventy volunteer men and women operating in three crews or watches. The building was intended to be able to operate for up to twenty-one days in case of a nuclear attack. It was responsible for establishing the exact position and height of all nuclear explosions by collating information gathered from the monitoring posts within its group area; for gathering data on radioactive fallout at each post, together with the subsequent dose rate readings; the interpretation, and dissemination of the data to the Southern Sector Control at RAF Rudloe Manor, to adjacent Group HQs, Regional Seats of Government (RSGs), the emergency services, and the armed forces; and initiating the warnings of the imminent danger of radioactive fallout.

Over time, the methods of plotting, and the communication equipment used changed, but the Group’s role remained the same until the stand-down in September 1991. A skeleton staff was retained at Exeter until 1992, to oversee the de-storing (removal of equipment) and the closure of all of the Group’s buildings in readiness for their eventual disposal. After closure in 1992 the Group HQ was on occasions used by the Devon and Cornwall Police for training purposes, and was sold into private hands in September 1999. The building stood empty for a number of years before becoming a laser questing centre in 2006.

Reasons for Listing

The former ROC Group Headquarters, Exeter, completed in 1962, is designated at Grade II for the following principal reasons:
* Rarity: one of only two surface-type Royal Observer Corps Group Headquarters surviving in England;
* Architectural interest: a building which expresses through its monumental and robust construction the threat posed by the atomic bomb and the necessary measures to protect its occupants from the effects of nuclear attack;
* Intactness: an intact early 1960s surface-type Royal Observer Corps semi-protected group headquarters, that has experienced only limited alteration since being built, retaining its original external appearance, internal floor-plan and some fittings;
* Historic interest: is representative of the Royal Observer Corps’ key role of nuclear monitoring and reporting during the Cold War, contributing to the British Government’s intention of providing sufficient warning to the public to take cover from the effects of nuclear radioactive fallout.

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