Built-in 1952, Kelvedon Hatch Bunker was designed to house up to 600 military and civilian personnel who would organise the population’s survival and continue Government operations in the event of a nuclear attack. Nestled deep in the Essex woodland, it was hidden from the World and only revealed to the public in 1992 when it was decommissioned.

The bunker is built 125 feet (38m) below ground and entered via a standard-looking Bungalow set amongst the trees. The Bungalow leads to a service tunnel measuring 91m, above which there are two different levels containing generator rooms, command centre posts, dormitories and a hospital wing. The building was fully manned until its closure in 1992.

Kelvedon Hatch is a village and civil parish in the Borough of Brentwood in south Essex, England. It is situated just north of Pilgrims Hatch, approximately 4 miles north of Brentwood and surrounded by the Metropolitan Green Belt. Today, the village is no longer a rural backwater, with many of its population commuting to work elsewhere. It has a population of 2,563.

It is home to the Kelvedon Hatch Secret Nuclear Bunker, the largest and deepest cold war bunker open to the public in South East England. Hidden in a wood off the A128 Ongar Brentwood Road is a small bungalow (guardhouse) that hides a three-level bunker complex 125 feet underground; a long corridor leads down to a place where up to 600 people would have been confined behind blast-proof doors in the event of a nuclear war. The bunker was built in 1952/3 by Peter Lind & Company Ltd as part of ROTOR, an urgent government building programme to improve Britain's air defence network. It became the Sector Operations Command for the RAF Fighter Command, responsible for the London Sector. It subsequently became a potential 'regional government bunker' as the threat of nuclear war grew in the 1960s.

The bunker was sold in the 1990s and is now a tourist attraction and film location. The bunker is owned and operated by the family who originally owned the land before the military moved in. It has many historical items remaining intact, including a BBC studio. A souvenir shop in the original canteen sells items, including government literature produced for the public in the early 1980s.

The name is recorded as Kelenduna, Kalenduna and Kelvenduna in the Domesday Book, meaning Speckled Hill. From its early days in the Mediaeval period until the mid-20th century, the main activity in Kelvedon Hatch was agriculture. Records from 1871 show 82 households, of which only 3 'white collar' households and 4 landowners or independent means, with the rest engaged in a local agricultural economy. However, many younger people gravitated towards the main towns during the Victorian years, encouraged by railway links at Ongar and Brentwood.