Fort Bembridge was one of the Royal Commission Forts built between May 1862 and July 1867 at a cost of £48,925. Although built as a land fort it was intended to be the defence of last resort in the event of any enemy landing in Sandown Bay. It had accommodation for one hundred and ten men, including four officers. The initial armament was six 7-inch RBL guns, although there were emplacements for ten guns. Built on a hill top it has a deep dry moat and covered way running around the outside. There are twelve crotchets (traverses) along this covered way to prevent direct enemy fire along this defence line. There are also three double caponiers and these are supported by strong points for infantry musketry fire at each of the six corners of the scarp wall.
In 1893 the six 7-inch RBL guns were were replaced by 64-pdr 71cwt RML guns on 6 foot parapet carriages and two 4-inch BL guns on siege travelling carriages. The 64-pdr guns were removed in 1900 and the 4-inch guns three years later.
Fort Bembridge as a test facility for submarine and torpedo defences between 1880 and 1900. This primarily involved two cables running from the fort to the sea used to detect any metal passing over them. A forerunner of the World War 2 Indicator Loops. The Fort was also used for a Battery Command Post and Position Finding Station for the 9.2-inch Culver Down Battery which stands 500 metres to the South-East. This fire control position was used to coordinate fire from both Culver Down Battery and the 9.2-inch Battery at Nodes Point.
During World War Two a pair of Allen Williams turrets were installed on the ramparts.
Grateful to Alistair Graham Kerr for help with some images.