File:Control rooms - geograph.org.uk - 1114585.jpg

English: Control rooms Two old WW2 Nissen huts near East Pitcorthie now used as farm sheds. These have quite a distinguished history. They were erected during WW2 by Naval Intelligence and were the control centre for a group of five secret direction finding wireless stations in the surrounding fields. The task of the naval signals officers and WRENS in these huts was to obtain accurate “fixes” on U-boats and enemy surface vessels from their radio transmissions. There were two similar d/f installations stations, one near Dunmow in Essex and another at Goonhavern in Cornwall. When a transmission was detected, all three groups were alerted and they provided bearings which pinpointed the location of the source of the transmission. (There were many other secret listening and d/f stations around the UK but only at these three sites were groups of five stations used for maximum accuracy.) The Nissen huts in the photograph were manned 24 hours a day. The naval staff co-ordinated the incoming requests and fed back the results to their central command using teleprinters over secure telephone lines. There is still an identical pair of Nissen control huts near Dunmow and traces of the d/f stations are still visible in the fields around Goonhavern.