It is a flat, raised area of marshland around 2 kilometres (1.2 mi) long and 1 kilometre (0.62 mi) wide among the tidal sand banks on the southern side of the estuary and separated from the British mainland of Chetney Marshes by a narrow channel known as Stangate Creek.

In the late 18th and early 19th centuries it was used as a quarantine base for disease-infected ships, with the bodies of those who died usually buried on Deadman's Island 3 kilometres (1.9 mi) to the east.

In the first years of the 19th century, Burntwick became a hideout of the North Kent Gang, a notorious group of smugglers.

The majority of the fifty-strong group were eventually captured with three executed on Penenden Heath near Maidstone and a further fifteen transported to Tasmania.

[2] The island then became the property of the Ministry of Defence and a battery was built there, later joined by a torpedo school and barracks during the Second World War.