During World War II, as the Nazis seized power over Europe, it dawned on the British War Office that an invasion was looking increasingly likely, and the coastline of the United Kingdom was nowhere near ready to defend against it, particularly around the River Crouch Estuary. The War Office set out to arm the undefended area with the quick construction of pillboxes as well as laying mines and booms in the estuary. But that seemingly wasn’t enough; In 1941, the minefield was expanded and a control tower was constructed to…