The fort was originally designed by Captain William Crossman, with later modifications by Captain (later Maj General)
Edmund Frederick Du Cane, Construction commenced in 1859 and was completed in 1865. When originally designed it had provision for 35 large guns. By 1893 the guns consisted of five
RBL 7 inch Armstrong guns and nineteen RML 64-pounders, together with a number of
32 Pounder Smooth Bore Breech Loading (SBBL) guns. It was also designed with barrack accommodation for 2,000 men in two-tiered casemates at the rear of the Fort. In the event, far smaller garrisons have been based there, with only six gunners in 1882. Early in the 1900s it became an infantry battalion headquarters with 14 officers and 423 other ranks, and from 1903 was used for rifle training. Tregantle is infamous within the armed forces because many of the rifle ranges located there slope steeply down towards the sea. These ranges are still in use, primarily by personnel located at
HMS Raleigh. Tregantle was vacated after
World War I until 1938, when it was used as the
Territorial Army Passive Air Defence School. During World War II it was used first as the Army Gas School and from 1942 as US Army accommodation. Since 1945 the fort, and the cliffs, beach and sea to the south-west, have been in use by the British Armed Forces. It is currently part of the Defence Estate and used for
Royal Marine training. It is also used by specialist Royal Naval
EW teams (FEWSG) for the monitoring of ship's communications in the area. FEWSG operate specialist coded transmission scenarios from Tregantle Fort and surrounding areas for Naval warships to decode at sea as part of an ongoing training schedule. In January 2020 a Royal Marine died in a training exercise off the beach. ==Tregantle Down high-angle battery==