A former Royal Observer Corps underground monitoring post located near Colchester, Essex, United Kingdom. This type of bunker was part of a nationwide network established during the Cold War to monitor nuclear explosions and radioactive fallout in the event of a nuclear attack on the United Kingdom. These small, reinforced concrete structures were typically staffed by three-person volunteer crews and equipped with specialized monitoring instruments.
The bunker network was operational from the 1950s until 1991, when the Royal Observer Corps was stood down following the end of the Cold War.