This WWI gun battery has fallen into the sea, the result of some serious coastal erosion. Even just standing there you can see the cliffs crumbling before your eyes. These photos show Al (Highy) who showed us around.
Details here from Pastscape;
Fort Godwin was a coastal battery built to defend the ports along the Humber estuary. It opened in 1915 and was constructed for two 9.2-inch guns. The battery was in use throughout WW1 and modified during the WW2. In 1940 it was equipped with a 4-inch gun and a new pair of searchlights.