The Central Government War Headquarters is a 240-acre 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.
Construction began in the late 1950s. Over a kilometre in length, 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.
The site was so top secret that many of the civil servants, who had been allocated a desk there, had no knowledge of it. Despite the fact that it became outdated shortly after it was built, due to ICBM nuclear missiles being able to target it, and the formulation of other plans (such as "PYTHON"), the site remained in operation for thirty years. At the end of the Cold War, in 1991, the still unused complex was taken over by the Ministry of Defence and kept on standby in case of future nuclear threats to the UK. Finally, in December 2004, with the underground reservoir drained, emptied of fuel and supplies, and with a skeleton staff of just four, the site was finally decommissioned.