A small circular structure, probably dating to the Second World War, adjacent to the Chattenden and Upnor Railway at Four Elms Hill, is visible on aerial photographs taken in the 1940s and 1950s, and has been mapped as part of the English Heritage: Hoo Peninsula Landscape Project. The structure was located at the edge of a wooded area on Beacon Hill, alongside the railway track about 30m to the south of a bridge which carried the railway over Ratcliffe Highway, and would have had a view of the bridge and possibly the road below. It was probably a circular pillbox, and was last visible on aerial photographs taken in 1950.