Here’s a little generic history shamelessly stolen from Wikipedia…
“Royal Observer Corps Monitoring Posts are underground structures all over the United Kingdom, constructed as a result of the Corps’ nuclear reporting role and operated by volunteers during the Cold War between 1955 and 1991.
In all but a very few instances the posts were built to a standard design consisting of a 14-foot-deep access shaft, a toilet/store and a monitoring room.
A third of the total number of posts were closed in 1968 during a reorganisation and major contraction of the ROC. Several others closed over the next 40 years as a result of structural difficulties i.e. persistent flooding, or regular vandalism. The remainder of the posts were closed in 1991 when the majority of the ROC was stood down following the break-up of the Communist Bloc. Many have been demolished or adapted to other uses but the majority still exist, although in a derelict condition.”