On May 3rd and 4th, a team of volunteers from the Dover Archaeological Group, Canterbury Archaeological Trust and the National Trust hand dug several excavation trenches at Fan Hole to ascertain where the early twentieth century sound mirrors which had been completely hidden since the 1970s were.
These acoustic devices were positioned around the south and eastern British coastlines and used as early warning devices to detect the engine noise of incoming enemy aircraft up to 8–15 miles away. Microphones were placed at the focal point, allowing listeners to hear the engines. However, they soon proved to be ineffective as 1930s high-speed aircraft passed over too quickly to detect and new technological discovery lead to the more efficient use of Radar.
From the work carried out in early May, it would seem that the Fan Hole sound mirror complex remains around 90% complete, preserved below dumped 1970s soil and rubble.
It looks likely that only fairly limited restoration work would be required to stabilise these structures and leave them open for permanent display as important structures in the story of the defence of Britain.
No further excavation will be made until a topographical survey and planning application has been completed.