Bath Stone is an oolitic limestone comprising granular fragments of calcium carbonate and was open cast quarried and first removed by tunneling underground at Combe Down and Bathampton Down and used in the construction of the city as we see it today. Revered for it’s pale colour, strength and ability to be finely carved relatively easily, whilst still retaining long term endurance when exposed to the elements.

In the early 18th century, Ralph Allen promoted the use of the stone in Bath itself, and demonstrated its potential by using it for his own mansion at Prior Park. Following a failed bid to supply stone to buildings in London, Allen wanted a building which would show off the properties of Bath Stone as a building material. He acquired the stone quarries at Combe Down, Odd Down and Bathampton Down.

Hitherto, the quarry masons had always hewn stone roughly providing blocks of varying size. The architect John Wood required stone blocks to be cut with crisp, clean edges for his distinctive classical fa├žades. Stone was extracted by the “room and pillar” method, by which chambers were mined, leaving pillars of stone to support the roof. Allen built a tramway from his mine on Combe Down which carried the stone down the hill, now known as Ralph Allen Drive, which runs beside Prior Park, to the river Avon near the centre of Bath.

John Wood was the architect responsible for most of the famous buildings in Bath and it was during this period that buildings such as The Royal Crescent were built. As yet efficient transportation of the stone had not yet begun so most of the stone quarried from the area was used locally although some was transported on the River Avon. After Ralph Allen’s death in 1764 the quarrying continued on the Downs but the stone was gradually being exhausted.. When the Kennet and Avon canal was built in 1810 the stone was moved further afield and other mines were opened up in the area.

When Box Tunnel was dug in 1838-1841 further good quality stone was discovered in vast beds leading to more discoveries in the Corsham and surrounding areas which led to the bath stone ‘goldrush’ around 1900 when about 3,000,000 cubic feet per annum was being extracted underground.

No mine abandonment plans of either the tunnels or the caverns, known as voids were made, which led to a vast network of passageways left behind, often filled with waste stone offcuts known as ‘deads’ Inside the quarries the walls and pillars of the are studded with pick and tool marks, and show evidence of the use of huge stone saws, all of which bear testimony to the variety of techniques used to extract the stone over the mine’s three hundred-year history.

Following their closure and abandonment, the mines were latterly used for a variety of purposes, including a mushroom farm, and as air-raid shelters during the World War II Baedeker raids on Bath. During the 1930s there was a recognition of a need to provide secure storage for munitions in the south of the United Kingdom, and a large area of the quarries around the Corsham area was renovated by the Royal Engineers as one of three major underground munitions stockpiles in the area. This ammunition depot was serviced by a spur railway line from the main London to Bristol line, branching off just outside the eastern entrance to Box Tunnel to an underground station also build inside the old quarry. A further 2200 yard long tunnel was constucted from the main line railway to Monkton Farleigh so as to transport ammunition safely and out of sight from above.

A portion of the underground quarry complex was developed as a ‘shadow factory’ for aircraft engines, to act as a fallback should the Bristol Engine company factory at Filton be taken out of action by hostile bombing. In practice this factory which cost tens of millions of pounds to build employed 16,000 workers on a shift system yet only produced 100 Bristol Centaurus aero engines. After the war, British defence doctrine during the early Cold War period indicated a requirement for a fallback location for central government outside London, to assume national control in the event of London being destroyed by the newly developed atomic weapons. The quarry complex at Corsham was chosen for this location and development of the site commenced in the 1950s. In the event of an imminent nuclear attack, it was assumed that the government would be evacuated from London by rail or helicopter. The facility would provide a safe haven for the Prime Minister, the Cabinet, commanders of the Royal Air Force, Royal Navy, and British Army and supporting civil servants and military personnel. Facilities inside the complex included accommodation and catering for nearly 4,000 people, including a hospital, organic electrical generation and the ability to seal the complex from the outside environment, contaminated by radiation or other threat. The bunker facility was known by various code names over the period, such as Stockwell, Turnstile, and Burlington was never manned or put into action and was infact not fit for purpose since the advent of thermo-nuclear weapons a few years after the bunker was completed. The site was decommissioned and placed in a state of care & maintenance in the mid 1990s following the fragmentation of the Soviet Union and the end of the cold war and later de-classified in 2005

Another military use for the underground space during the war was by the Royal Air Force who established the Headquarters of No 10 Fighter Group, Royal Air Force in an adjacent quarry. RAF Box was later renamed RAF Rudloe Manor and expanded to encompass a number of communications functions, including No1 Signal Unit, Controller Defence Communications Network, No 1001 Signal Unit Detachment and Headquarters RAF Provost & Security Service. No1 SU and CDCN were both housed in bunkers within the quarry complex, which also included an RAF Regional Command Centre for the South West of England.

A non military use during the war other than air raid shelters was by the London art galleries for the storage of paintings and other works of art, away from the Blitz bombings. They used quarries at Westwood near Bradford on Avon for this purpose along with other dispersal sites around the country

The military still have a presence underground such as the Corsham Computer Centre which was built into part of the disused ammunition depot during the 1980s and current examples of other uses include not only defence establishments, but also a secure bonded wine warehouse at Eastlays (near Gastard) and facilities for Wansdyke Security Ltd. which specialises in storage and retrieval of documents, film, magnetic media, computer data, microfiche and microfilm in underground vaults, giving protection from fire, flood and terrorist attack.

Underground extraction of Bath Stone continues in the Corsham and Ridge areas but on a smaller scale than previously, and is highly mechanised. Also at the Stoke Hill quarry near Limpley Stoke. There is now a strong demand for good quality Bath Stone for restoration work and new buildings to match exisiting nearby constuctions.

Up to 10% of the total British population of greater horseshoe bat use the quarries at times, and a maximum of 230 individuals of the species have been counted. The Lesser Horseshoe Bat also uses the mine, as do the four Myotis species: Whiskered, Brandt’s, Natterer’s and Daubenton’s bats.