The Mistley Anti Aircraft Operations Room was built in 1951 for the Royal Artillery (War Office), it is built to the standard design with one floor and both entrances above ground and the other floor below ground.
The Bunker was sold to Essex County Council in 1963 for £5250 (It had cost £500,000 to build in 1951) and it became one of 4 sub-controls (the others were at Harlow, Chelmsford and Billericay) reporting to the County Control at Chelmsford. This was located in the basement of the new County Hall extension which opened in 1961 and before that in the basement of the old County Hall where it had been located in WW2. The 1965 Essex war plan records Mistley as being the NE Essex Sub County Control (AK) reporting to County Control 42A at County Hall. By 1966 Mistley became the main HQ for the County as the proposed Chelmsford HQ had not been built. From 1968 until the early 1980’s Mistley was placed on care and maintenance an in 1984 it finally became the county standby when the County opened the long overdue new control centre in County Hall. (another part of the new extension basement) The Bunker remained fully operational until 1993 when it was de-commissioned at the end of the ‘Cold War’.
In 1995 the building was leased to the Bunker Preservation Trust, the same team that had helped set up the WW2 war rooms (Hellfire Corner) at Dover castle, Liverpool’s ‘Western Approaches’, the Battle of the Atlantic War Room and Scotland’s secret nuclear bunker at Anstruther. Mistley was renovated and refurbished and opened to the public in Easter 1996 and after 6 successful years closed its doors for the last time after a free public open day on 1st December 2002.
All the plant is still in place including the standby diesel generator (a 1980’s replacement), ventilation and filtration plant and the boiler.
The 1950’s army camp to the rear of the bunker has been gradually removed over the years and replaced by playing fields, a car park and a new village hall although some faint traces of the camp are still visible.
Those taking part in the visit were Nick Catford and 40 other members of Subterranea Britannica.