The sound mirrors, or “listening ears” at Greatstone, near Dungeness, are one of Britain's strangest and most atmoshperic pieces of industrial heritage. Built between 1928 and 1930, they were part of an experiment in detecting aircraft approaching across the sea.
This panorama shows the setting sun peeking through the control window in the 200-foot mirror. The 20- and 30-foot mirrors can be seen to the right.
Never highly successful, by 1935 they were rendered obsolete by the emerging technology of radar. After World War II, orders were given to destroy the sound mirrors, and explosives were detonated on one of the buttresses on the back of the 200-foot mirror. However, British concrete proved tougher than expected, and the blast only succeeded in blowing a small hole in the buttress. After that, the order for destruction was - thankfully - withdrawn for some reason, and the mirrors have been left at the mercy of the elements, the shifting shingle of what has since become a gravel pit, and more recently, vandals.
In 2003, English Heritage undertook some conservation work and installed interpretation at sites from which there is a view of the mirrors, along with security measures. The mirrors themselves are located on an island to which there is no public access, except on guided walks arranged several times a year by the Romney Marsh Countryside Project
. They’re well worth a look.
More information on the sound mirrors can be found on Wikipedia
and Andrew Grantham’s web site
There's another panorama
of the mirror on my web site, and some photographs on Flickr