MY ASSISTANT had told me I could get to Greatstone-on-Sea via the Romney, Hythe and Dymchurch Light Railway (steam traction), but it was not running the day I went so I used my bike instead. Whenever I visit the English seaside it always seems to be the off- season. I sometimes wonder whether they deliberately close everything down at the sight of strangers.

Greatstone-on-Sea was no exception. Nowhere was open.

I had come to the south- east Kent coast to see the Greatstone-on-Sea Listening Device, a curving concrete wall 200ft long and 25ft high, facing out to sea. Built in 1928, it was designed to detect the sound of enemy aircraft and shipping up to a distance of 12 miles.

Whether it would have been successful is unclear: according to my assistant's research, experiments at the time were inconclusive. There were even claims that the naked ear was more effective. Then radar was invented within a few years of its completion and rendered it obsolete. It stands among vast gravel workings which stretch away towards Dungeness. For many years the area has been inhabited by geese and other wildfowl. Now it is being dug up by a gravel company.

I parked my bike in someone's garden and trudged with difficulty across the gravel. The Listening Device waited in silence beside a huge, water-filled gravel pit. At last I stood before it. I tried to imagine the roar of approaching Messerschmitts. But all I heard was the splashing of geese.

The Greatstone-on-Sea Listening Device is at OS Grid Reference TR 075215.

(Photograph omitted)