Central Government War Headquarters

[7] Over 1 kilometre (0.62 mi; 3,300 ft) in length, and with over 60 miles (97 km) of roads, the site was designed to accommodate the Prime Minister, the entire Cabinet Office, other civil servants, and domestic support staff.

The underground city was equipped with all the facilities needed to survive: from hospitals, canteens, kitchens and laundries to storerooms for supplies, accommodation areas and offices.

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 throughout the complex, using compressed air.

[10] To maintain the secrecy of the site, even during a countdown to war, it was envisaged that 4,000 essential workers would assemble at an outlying destination known as Check Point.

[23] At the end of the Cold War, in 1991, the rest of 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.

[2] In October 2015, certain areas of the complex including the telephone exchange were put on the Historic England "At Risk" register due to their immediate threat of being lost or damaged beyond recognition.