Royal Observer Corps monitoring post

Royal Observer Corps monitoring posts are underground structures all over the United Kingdom, constructed as a result of the Royal Observer 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 (4.3 m)-deep access shaft, a toilet/store and a monitoring room.

Source: Wikipedia — Royal Observer Corps monitoring post (CC BY-SA 4.0)