Sound Mirrors were an early warning device installed around the south coast during and after the First World War to detect the approach of enemy aircraft. Known as ‘whisper dishes’ or ‘listening ears’, they were concave concrete constructions often with a microphone at the front to amplify the sound caught by the dish. Quaint as they now seem, and by the 1930s the increasing speed of aircraft made them of limited use, the system of linked stations for plotting aircraft movements they formed was adopted by the radar system that replaced it.

In 2014, the National Trust excavated the area in and around the deep shelter of Fan Bay - a section of land along the White Cliffs of Dover - to uncover a pair of Sound Mirrors. In the late 1970s Dover Council had buried and backfilled the entrance to the underground shelter and entombed the Sound Mirrors in hundreds of tonnes of soil topped with chalk as part of a designated ‘eyesore clearance programme’.

The ‘eyesore clearance programme’ had been intended to destroy all trace and reminder of both world wars, but actually it created a time capsule that preserved the deep shelter, the Sound Mirrors and its signs of human habitation.

Caves and tunnels are two-a-penny around the Dover coastline, but Sound Mirrors are like rare fossils. Fully exposed, the mirrors are monumental and elegant, combining these normally opposed qualities in the same way that the term ‘Sound Mirror’ combines sight and sound in a synaesthesia all its own.

The Sound Mirrors predated the deep shelter. The first, a prototype of the acoustic warning system, has a fifteen-foot radius and was installed during the First World War in 1917. The other, five foot larger, joined it in the late 1920s. The mirrors are not just quaint, like penny-farthing bicycles, but they work.

Leaving the Sound Mirrors of Fan Bay behind, it is possible to walk from the White Cliffs of Dover to Folkestone, crunching along the pebbles of Shakespeare Beach.

On the approach to the village of Capel-le-Ferne is another Sound Mirror. Unlike those at Fan Bay, this one stands on top of the cliff, isolated and exposed rather than dug into the side of a hill. It has stood here for nearly a century, cracked and weathered now, haggard and forlorn. There’s a photograph from the Second World War of Corporal Sidney Cocks of the 5th Folkestone Home Guard standing alone with a First World War Lee-Enfield Mk1 on these cliffs at Capel-le-Ferne, guarding the nation. From the shape of the cliffs, he must have been patrolling near the Sound Mirror.

The Mirror itself is much larger than Corporal Cocks, bigger than those at Fan Bay as well, but it too is dwarfed, by history rather than scale, a stone-age Sky dish out of time but still defiantly in place.

This article was edited by Kay Whalley: 8 October 2025.

Bibliography

Edmond, R. (2023). Borderland. Troubador Publishing Ltd.
National Trust. (2015). Fan Bay Battery Brief History. [online] Available at: https://www.nationaltrust.org.uk/visit/kent/the-white-cliffs-of-dover/fan-bay-battery—a-brief-history [Accessed 9 Sep. 2025].