Birtley, Royal Observer Corps Monitoring Post

Springwell ROC opened here as post 4 in cluster E of 30 Group in December 1940. In November 1953 it was renumbered as post 4 in cluster N of 23 Group. In 1954 the post moved to Springwell (HER 5879). This was a visual observation post to track aircraft movements. Early Observer Corps Posts had a simple instrument for plotting the plan position of the aircraft. Throughout WW2 the ROC had a more sophisticated "Post Instrument" which also recorded the height of the aircraft. WW2 posts were frequently simply sand bagged emplacements, or more sophisticated examples were of domestic brick construction, some two-storey, with an open observation post and a crew room. Some had latrines.