Central Government War Headquarters

The Central Government War Headquarters is a 240-acre (97 ha) complex built 120 feet (37 m) underground as the United Kingdom's Emergency Government War Headquarters – the hub of the country's alternative seat of power outside London during a nuclear war or conflict with the Soviet Union. It is located in Corsham, Wiltshire, in an old underground Bath stone quarry known as Spring Quarry.

The complex was known variously as "Stockwell", "Subterfuge", "Burlington", "Turnstile", "Chanticleer", "Peripheral", and "Site 3". It was also nicknamed "Hawthorn" by journalist Duncan Campbell, who first revealed its existence in his 1982 book War Plan UK. It was also mentioned by Peter Laurie in his 1979 revised edition of "Beneath the City Streets".

Construction began in the late 1950s. Despite becoming outdated shortly after it was built, due to intercontinental ballistic missiles being able to target it, and the formulation of other plans (such as PYTHON), the complex continued to have a role in war plans and the site remained in operation for thirty years.

Over 1 kilometre (0.62 mi) in length, and with over 60 miles (97 km) of roads, the site was designed not only to accommodate the then Conservative Prime Minister, Harold Macmillan, but the entire Cabinet Office, civil servants and an army of domestic support staff.

Blast-proof and completely self-sufficient, the complex could accommodate up to 4,000 people in complete isolation from the outside world for up to three months. The underground city was equipped with all the facilities needed to survive, from hospitals, canteens, kitchens and laundries to storerooms of supplies, accommodation areas and offices. An underground lake and treatment plant could provide all the drinking water needed whilst twelve huge tanks could store the fuel required to keep the four massive generators in the underground power station running for up to three months. And unlike most urban cities above ground, the air within the complex could also be kept at a constant humidity and heated to around 20 degrees Celsius. It was also equipped with the second largest telephone exchange in Britain, a BBC studio from which the PM could address the nation, and an internal Lamson Tube system that could relay messages, using compressed air, throughout the complex.

...
Wikipedia