Knock John fort is situated approximately 16.1 kilometres (9 nmi) from the coast off Essex and was grounded on 1 August 1942. It was decommissioned on 14 June 1945 and evacuated on 25 June 1945. The platform was maintained until May 1956 when it was abandoned. In 2009, it was observed that there was a slight distortion of the legs when viewing the tower from west to east. It is thought that underscouring is the cause of this.