Sound mirrors near Dover

The White Cliffs Underground website has photographs of the two mirrors just east of Dover. These are built in a different form to the others, being set into a hillside.

Location

The mirrors were at either Langdon Bay (somewhere near Grid reference TR345425) or the adjacent Fan Bay (TR352428). I think Fan Bay is more likely, and the Ordnance Survey map shows a path layout like the one on this map of Fan Hole Battery in 1943 and this overview map on the Dover Underground website.

I went to have a look around the area on 2003-05-24, but I couldn't spot many obvious clues to the exact location of the mirrors. I think I could trace the route of the 'ash path' at Fan Bay, and there is a hollow in the hillside approximately where one of the mirrors might have been. I found a small concrete block in the grass, which looked like a small dragon's tooth (pimple) anti-tank block. This could have been a stand for a microphone, but it seemed a bit smaller than at Kilnsea and didn't have a post in the top.

If you do know where the mirrors are (or were), please let me know.