If Napoleon had ever landed an invasion force on the Pevensey Levels he'd have found himself being irritated by the guns and garrison of the Eastbourne Redoubt- a fortress built on the western flank of Pevensey Bay in 1805. The Redoubt is circular and partially buried- with its main rooms and parade ground below ground level and only its gun platform exposed. It remained in the hands of the military- and was put to various uses by them- until after the Second World War.
The building now houses a military museum- and entrance to the parade ground and gun platform is free. The original guns have long since been dispersed and scrapped and the ones that now fill the embrasures are a job lot- scrounged from various sources and most of them very much smaller.