Summary
A part-inclined and part-vertical shaft, probably originally constructed to provide ventilation in Spring Quarry, Corsham in the C19. The shaft was modified and an escalator was inserted in c1943, to provide pedestrian access between the surface and the newly-installed Bristol Aircraft Factory in Spring Quarry. The upper, vertical section of the shaft was rebuilt and strengthened in c1961 as part of the construction of the Central Government War Headquarters (CGWHQ) in Spring Quarry.
Reasons for Designation
Slope Shaft (Emergency Exit) A in the CGWHQ, below MoD Corsham is designated as a Scheduled Monument for the following principal reasons:
* Period: it is testament to the importance of the subterranean aircraft factory in World War II, and secondarily to the perceived threat of nuclear strike that Britain faced during the Cold War;
* Rarity: this fortified access route is a bespoke construction specific to the CGWHQ;
* Survival: it retains the sub-structure of the escalator, the operational plant and the blast-proof doors;
* Group Value: the CGWHQ site is an unparalleled example of our national Cold War defence heritage, and represents the systematic use of expansive underground areas by industry and the military during the C20.
History
The Corsham Mines are a multi-layered historic site near Bath, beneath the southern end of the Cotswold Hills in Wiltshire. Quarrying of Bath Stone in the wider area took place from Roman times, and by the C18 Bath Stone had become a highly sought after building material. The opening of the Kennet and Avon canal in 1810, and the subsequent construction of the Great Western Railway in the 1840s, made the transportation of the stone to farther locations easier and cheaper, thereby increasing its popularity. Brunel's cutting of the Box Railway Tunnel, beside the village of Corsham, revealed a rich seam of high quality stone beneath the hills. Intense quarrying followed, leaving a network of quarries with worked-out chambers and air shafts, including Spring Quarry. By the time mining ceased in 1940, there were over 60 miles of tunnels across 3,000 acres, located at depths between 80 and 100 feet below ground.
The Bristol Aeroplane Company (BAC) at Filton, near Bristol was bombed in September 1940. In response, Lord Beaverbrook, of the Ministry of Aircraft Production (MAP), issued an urgent plan to relocate all production below ground, which was endorsed by Churchill. The limitations of time, suitable sites, and wartime resources quickly saw the scheme scaled back to the relocation of Filton's engine plant. In December 1940 four quarries were requisitioned by the Ministry, including Spring Quarry, to the south of the Box Tunnel. It covers a vast 3,300,000 square foot area (or 76 acres). It was intended that BAC would convert Spring Quarry for engine production in 6 months, at an estimated cost of £100,000.
However, the scale of the factory construction project was enormous, involving the removal of thousands of tons of rubble stone, the levelling of floors, and the strengthening of pillars and roofs using steel and concrete. Lifts, escalators, and an extensive ventilation system were installed. Furthermore, BAC became doubtful about the practicality of the project, and their involvement was scaled back. The factory was still not ready for use by the end of 1942, when German bombing had largely ceased, and the need for the underground factory programme had all but vanished. The MAP factory was reclassified as a shadow factory, and proposed production was switched from the Hercules engine to the less vital Centaurus. By 1945, the factory still fell short of its original specifications, and its cost had risen to many millions. Throughout the war, engine production figures were negligible, and the factory closed at the end of the war. MAP itself was abolished in 1946. Spring Quarry was bought by the government in 1954, when the north-east area was allocated for conversion to a secret CGWHQ, for use in the event of a nuclear war.
The first known planning for the dispersed operation of government departments, should Central London be destroyed through enemy attack, was during a sub- committee of the Committee of Imperial Defence under Sir Warren Fisher in 1937. Following the war, it was acknowledged that developments in weapons meant that the government's emergency plans were inadequate. In the light of the huge sums spent developing the MAP factory in Spring Quarry, estimated at £30 million, the Treasury proposed buying the requisitioned quarry for use as a citadel for future emergencies. However, the quarry was not bought from the Bath & Portland Stone Company until April 1954, along with 100 acres of land above ground. In 1957 the plans for the emergency headquarters were finalised; the site was intended to provide a safe haven from which the work of the Government could continue. From here, the reconstruction of the country following a nuclear attack would be overseen. It was designed to accommodate up to 4,000 military and government staff, including the Prime Minister and key cabinet officials. Occupants would be sealed underground for 30 days and co-ordinate with Regional Seats of Government around the country, meaning that extensive communications and welfare infrastructure was needed.
Work began in 1957 with the construction of a reinforced concrete wall separating the CGWHQ area from that part of Spring Quarry used by the Admiralty. Three blast doors were installed around the perimeter, and new ventilation shafts were created and reinforced. Five heavy duty goods lifts were installed and a ventilation system of 21 air shafts and 15 fans, some 15ft in diameter, was powered by two underground boiler houses. In order to facilitate the use by 25,000 staff, four high-capacity passenger lifts and two escalators were installed, including that in Slope Shaft A, the subject of this report. The upper, vertical part of Slope Shaft A was rebuilt with thick blast walls and ceilings, and concrete spiral stairs with railings. The original small buildings at ground level providing entrance to the shafts were replaced by new concrete bunker-like shaft-heads. Due to war shortages the escalators had to be requisitioned from London Underground, who agreed to wait for additional units that had been planned for installation at St Paul's and Holborn stations. The escalators were installed in early 1943 by the Waygood Otis escalator company. Slope Shaft A contains the No. 4 escalator from Holborn, which was shorter in length than the incline shaft it was to climb. Therefore, vertical shafts meeting the escalator at its highest point were constructed to house a stairway up to ground level, and power-generation equipment.
The incline shafts with fitted escalators, now known as Slope Shaft (Emergency Exit) A and C, continue to function as emergency exits from Spring Quarry.
The CGWHQ complex was never needed or used for its intended function, and was reduced in capacity over a number of phases during the late C20. The site was de-commissioned in the early 1990s. It was de-classified in 2004.
Details
PRINCIPAL ELEMENTS: a part-inclined and part-vertical shaft providing pedestrian access from ground level down to Spring Quarry, comprising an escalator, rising the length of the inclined shaft, with an open-well stair rising the remainder of the distance to ground level, via a vertical shaft. The inclined shaft rises from approximately 35m below ground, terminating at ground-level via vertical shafts adjoining the incline, on an east-west orientation
DESCRIPTION: the base of the escalator is reached via a painted brick foyer and rises through a vaulted, vertical-walled, reinforced-concrete tunnel. The original wooden treads on the escalator have been removed and replaced with anti-slip surfacing. There are tubular metal handrails running its length. The running machinery is exposed. Below and to the right of the escalator a set of concrete stairs rises up the sloped shaft, providing access for maintenance of the machinery. Lighting and electrical cabling are attached to the side walls.
The top of the escalator terminates within the first of two adjoining circular shafts. Circular rooms below and above the escalator head contain the machinery to drive the escalator, and Crompton-Parkinson power generation equipment. The adjoining shaft contains a wide, open-well concrete stair rising six flights, with a tubular metal handrail. The top of the stairs leads to two airlock chambers separated from the shaft by double sets of steel blast doors, intended to provide a barrier against potential contamination in the event of nuclear attack, thereby maintaining a safe environment within CGWHQ.
All above ground structures are excluded from the scheduling. The scheduled area includes a 1m margin on all sides as well as above and below.
