A former Royal Observer Corps underground observation post was located to the south-west of Billingborough. The post is believed to have been opened in 1963. Access was through a 2ft square hatch on the surface, where an associated air vent would have been visible. A ladder would lead down the concrete shaft to two rooms; the first being quite small and used to house the chemical toilet. The second, much larger monitoring room measured approximately 15' by 7'6'', and would have been staffed by three observers. The post remained in use until 1991, when it was closed and demolished shortly afterwards. {1}