[1][2][3] Naturally inaccessible from the north and east, the south and west sides were protected by the digging of a large ditch.

[5] The citadel was designed with open gun emplacements on the north, east and west sides.

[1] During World War II, a Chain Home Low Radar set was installed within the citadel, and the main magazine became a hospital.

[11][12][13] The railings at the approach to the north entrance form part of the original construction and are Grade II Listed.

[20][21] The Verne High Angle Battery was built in 1892, approximately 150 metres south of the citadel's southern entrance, as part of Britain's Coastal Defences.