Western flank and rampart

Along the top of the cliffs on the west side, between the West Bastion and Northwest Redan, is a 5.5-m- thick (18 ft) curtain wall that provided protection from attacks on that side.^[2] Quarrying also steepened the cliffs.

East Rampart

A curtain wall, similar to the one on the west, provides protection to bombardment from the east. The East Bastion and south redans are positioned behind this wall. The height of this rampart allows for a view to the southeast coast of Jersey, including a view of Icho Tower, a Martello tower built around 1811.

Bastions, redans, ditches and glacis

Two bastions are at the fort, one facing west and the other facing east, and four redans, two to the south, and two at the north end. Cannons placed in these areas would have been able to target forces attacking Fort Regent from any direction. The redans are not typical examples because they have more than two sides, are closer to demi-bastions, as seen in hornwork.

The fort has one 210-m-long (689 ft) glacis at the south end, which is a flat, sloping open area of grass, known as the Glacis Field.^[2] The only road and foot access to the fort is in this area; all other sides are very steep or vertical cliffs.

The East Ditch has a masonry-faced counterscarp and scarp, with a further outer ditch in the form of a large cutting. The Jersey Eastern Railway enlarged the cutting in 1873 to use it as a train station.

Cannons

Positions and embrasures for 100 cannons are in place within the fortress.^[2] However, a report dated 8 March 1810, counts only 55 cannons and six mortars at Fort Regent.^[2]

Water well

This section needs additional citations for verification. (December 2022)

No well existed on the hill, so between December 1806 and October 1808, a deep well-shaft was sunk into the notoriously hard Jersey granite to a depth of about 71 m (235 ft)^[2] by blasting a shaft of an average diameter of 8 ft with gunpowder charges. The Fort Regent well is believed to be the deepest well-shaft in the island [excluding artesian bores], and is a stunning tribute to the persistence and ingenuity of Georgian military engineers.

When the sappers and miners blasted through to the spring, at a depth of 221 ft below the well-curb in the underground well-head chamber, they did so unexpectedly and water rose rapidly in the shaft. The miners were hanging in a basket halfway up the shaft. The major of engineers in charge of the works recorded that "great difficulty was experienced in recovering the men to the surface before they were drowned by the inrush from the Spring". The construction records, including the commanding officer's daily diary, are now in the National Archives at Kew and were researched by the architect and the main contractor – C.G. Dumond (Builders) Ltd. – for useful information during the conversion of the fort into a leisure centre in the 1970s.

The granite was drilled with "jumper drill" irons hit with sledgehammers. As originally commissioned, water was raised to the surface by an above-ground horse whim or capstan at parade-ground level, but this proved to be both time-consuming and unpopular with the soldiery and lasted for only a year after the official opening in 1814. The first rocking beam pumps, operated in series all the way down the well-shaft by one long pump-rod, and operated by a man-powered capstan through a line shaft and gearing, was delivered and installed by Henry Maudeslay and Son in 1815, in a double circular underground chamber excavated just below the level of the parade ground. One chamber contained the capstan and connected to the adjacent chamber which contained the well-head machinery, and the mouth of the shaft. At some later time, the man-powered capstan was converted to operate by donkey power. This method, too, proved less efficient than was thought desirable; it proved difficult to get the donkeys into and out of the chambers through the long, sloping tunnel which originally began at ground level in the East Bastion, The motive power was changed again to be provided by a small steam engine. The steam engine, in turn, gave way to a gas engine, which is still in-situ, a rare survival of that late-Victorian technology, along with Henry Maudeslay's original well-head machinery from 1815.

During the 1970s reconstruction, the local government's client organisation – the Fort Regent Development Committee (FRDC) ordered that all of the well-shaft access ladders, cast-iron floor-gratings (supplied from Ironbridge by order of the War Office), and pump rods and valves – should be removed from the well-shaft and scrapped,^{[citation needed]} "because the Fort requires the well-water to be used for commercial and domestic supplies within the new leisure complex, and contamination from this old machinery cannot be risked". This act of "cultural vandalism" was carried out under the supervision of the clerk of the works, Mr. Greenwell, which was protested by a few knowledgeable persons at the time, but the reconstruction contract was politically sensitive; knowledge of the machinery's destruction and scrapping was limited to members of the managing FRDC, and to the project architect and main contractors' staff. So, the general public of Jersey, who might have expressed their concerns, never became aware of the destruction until long after the fact: even now it is not common knowledge amongst those who care about preserving as much of Jersey's historic past as possible. Though the main contractor salvaged all the recovered machinery parts, and handed them over to the client, as required under the construction contract for "all antiquities recovered from the Site", the Fort Regent authorities scrapped them two years after contract completion as being "of no historic interest and not worthy of preservation".

Access to the underground well-head and machinery chambers down a steep set of concrete steps and a steeply sloping tunnel is deemed too dangerous under modern health and safety concerns, this historic 19th-century well-head machinery seems doomed to be forever hidden away from members of the public. During the clearing and cleaning of the well shaft in 1979, the main contractor discovered a 40-ft-tall flat sheet of granite caused by a natural fracture plane that formed one face of the shaft about 100 ft below the surface. It was so hot, water dripping onto it from further up the shaft turned to steam, hot enough to blister a bare hand accidentally brought into contact with the granite surface. This may be the only example in the island of geothermal heat.

German occupation

During the German occupation of the Channel Islands, the German forces made additions to the fort, including platforms for flak cannons. Some of these concrete structures remain to date.

Storage

After the German occupation, the fort was used as a storage area for potatoes, wine, and coal.^[6] The nearby power station was coal-fired at the time.

Leisure centre

In December 1967, States of Jersey made a decision to adapt the site into a leisure centre.^[7] The swimming pool located on the glacis field, which opened in 1971 and closed in 2009,^[8] was the first modern addition to the fort. Demolition of its roof and flattening of the site will be completed in early 2021.^{[9][needs update]}