RAF Kelvedon Hatch is a former RAF Sector Operations Centre (SOC) located in Essex, north of London. The structure was built in 1952-53 as a 3 level hardened command bunker for the Metropolitan sector of Fighter Command. It is built in a similar method to all the other styles of ROTOR bunker, it is around 120 feet underground and is accessed via a standard ROTOR pattern guardhouse and entrance tunnel that enters the bunker on the lowest level.
The bunker operated in its original ROTOR role during the 1950’s before being repurposed in the 1960’s as a Civil Defence Centre, after that becoming a Regional Government Headquarters (RGHQ 5.1) – a function it continued in until it was closed and sold off in 1992, at which point the original landowners (the Parrish family) purchased it off the government and turned it into an excellent cold war museum and venue.
Their excellent website is here – www.secretnuclearbunker.com – and TheTimeChamber can throughly recommend a visit, you will NOT be disappointed! (NB* to take photos in the bunker you have to pay a fee and sign a not-for-commercial use waiver)