Castle Rock BatteryFlat Holm Island Lighthouse, United Kingdom
Castle Rock Battery is the most northerly of the four batteries on Flat Holm Island. There are three Moncrieff gun-pits, the central one being open to the rear. Each pit mounted a 7-inch RML Mark III gun on a disappearing mount. In the gorge there is an underground magazine with integrated earthen banks running back behind it to protect the landward approaches. The magazine is in reasonable condition although with some World War 2 modifications.
A contemporary diagram of a disappearing mounts used on Flat Holm can be see here.