Part of a seaward fortification begun in 1699 much damaged by modern buildings, particularly the western half, although its form is still visible. At the end of the 19th century a battery, Alemarle Battery, was built on the eastern half. The surviving features include:

At the very western end is a brick cartidge store which has a slightly chamfered roof of early concrete, linking it to 6 pdr QF (quick firing) guns. A room dug into the rampart below has three windows and a door set in a stretch of vertical wall within the sloping main revetment. The windows have iron frames with roses on the intersections oif the glazing bars. Ventilation bricks round the door indicates an air space in the wall. The concrete roof "burster" slab projects slightly and has a cambered top. This room was probably built in the 1880's and although now referred to as "The Bunker" is labelled on the 1899 plan as the north test room, a control centre for a submarine minefield (1).

From the National Heritage List for England:
17th Century Defences: surviving portion of late 17th century fortifications designed by Sir Bernard de Gomme. Stretch if indented trace east of Garrison Point Fort. Largely faced in Portland ashlar to cordon. The brick parapet is later and together with the rampart had been remodelled and mutilated by 19th century gun positions. At three angles are moulded corbels which carried sentry boxes.

Historic England archive material (2)

<1> Royal Commission on Historic Monuments in England, 1995, Sheerness: The Dockyard, Defences and Blue Town (Unpublished document). SWX6974.

<2> Historic England, Archive material associated with the Sheerness Lines (Archive). SKE56321.