Longdown Lane Shelter (now sealed) was one of five built by Surrey County Council in World War II. It was completed in 1941 and was mostly in unlined chalk. The site included a canteen, lavatories, and medical-aid post. One particularly unusual aspect is that in order to test the stability of the construction, a 550 pound German bomb was exploded at a depth of 23 feet on 10 June 1941. This was around 18 feet above the tunnels, which survived intact apart from a little fallen chalk (as did the mice and canaries which had been placed in the tunnels!).
Subterranea Britannica gained permissiin from the golf club which now occupies the site to try and locate the shelter in the early years of this century but despite hiring a mechanical digger were not able to find any trace.