Work started on the main part of the fort in 1861. Originally intended to have two stories of casemates like Fort Picklecombe, the design was altered during construction to a single story of 23 granite casemates with armored shields.
It was designed by Major (later Maj Gen) Whitworth Porter , and was built by George Baker and Company. The casemates were arranged in an arc and initially housed 22 9-inch Rifled Muzzle Loaders (RMLs) and one 10-inch RML gun, with accommodation for 180 men.
Underground there are large deep tunnels to store artillery ammunition safe from enemy gunfire. It was completed in 1869.
By 1880 the armament included 14 10-inch and nine 9-inch RML guns. By 1893 it mounted 14 10 inch Rifled Muzzle Loading Guns, eight 9-inch Rifled Muzzle Loading (RML) guns and six 6 Pounder Quick Firing (QF) guns.
In 1898 Six 12-pounder quick-firing guns were installed. By the early 1900s, the original armament was obsolete and was removed.
A three-story observation tower to direct the fire of these was built at the same time. The following year a Bofors 40mm anti-aircraft gun was installed.
On the dissolution of coast artillery in 1956 the Ministry of Defence abandoned the fort. In 1970 a lease was granted and the fort was converted into a national commercial diving school and scuba diving center.