 A brick observation post on the roof provided range-finding, and two remotely controlled searchlights installed on the roof of the north caponier could illuminate the riverside below.The purpose of these installations was to protect against raids by cruisers and torpedo boats and to counter any landings in the Thames.The fort's defences were also enhanced with two light anti-aircraft guns, including a Bofors 40 mm gun installed on the roof in August 1943, while the fort's perimeter was surrounded by barbed wire and trenches.