The Royal Commission on the Defence of the United Kingdom, which Lord Palmerston had established in 1859 in response to a perceived threat of invasion by Emperor Napoleon III of France, recommended the fort's construction.

When considering the defence of the Royal Dockyard at Pembroke Dock and the anchorage at Milford Haven, the Commissioners believed that there was a danger that an enemy force might conduct an amphibious landing on a beach on the southern Pembrokeshire coast followed by an overland attack on the naval facilities.

The entrance at the western (landward) end of the fort is approached by means of a drawbridge over a dry ditch and is defended by two caponiers or "flanking galleries", each of three storeys pierced with loopholes for small arms fire.

[1] In 1895, control of the fort passed to the Royal Naval Reserve, who emplaced a single BLC 5-inch gun on a "Youngman’s compression platform", apparently for training purposes.

[c][3] In 1914, the fort was purchased by J. P. James for £2000[d] on behalf of Edward Windsor Richards, a wealthy steel merchant, who converted it into a private house for the use of his granddaughter, Lillian Windsor-Richards.

[2] In May 2015, Pembrokeshire Coast National Park Authority approved an application to reopen the site to the public due to the economic benefit that it would bring to the area.