RAF Topcliffe is a Royal Air Force station in North Yorkshire... Topcliffe opened September 1940 as a bomber station in RAF Bomber Command, home to 77 and 102 Squadrons. Concrete runways were added in mid-1942, and 419 and 424 Squadrons (RCAF) moved in flying Wellington bombers and later, the Halifax III. On January 1, 1943 the station was transferred to No. 6 Group RCAF and became a training station. One of the substations was Dalton. Topcliffe and substations was designated as No. 61 (Training) Base in late 1943.

Source: Wikipedia article: http://en.wikipedia.org/wiki/RAF_Topcliffe