This List entry does not comprise part of an Asset Grouping. Asset Groupings are not part of the official record but are added later for information.

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The strategic position of Portsmouth, vital for the defence of the Channel coast and supporting a major naval dockyard, has led to the development of extensive and complex systems of fortification. Many owed their design and construction to periods of political unrest within Europe, or to specific threats of invasion, both real and imagined. Their development can be seen as a response to the sometimes rapidly changing nature of warfare and, in consequence, many were obsolete by the time that they were completed. Portsmouth is one of four locations in England where there has been continuity of fortification over at least five centuries. Of these, Portsmouth has the most widespread defensive network and shares, with Plymouth, the greatest concentration of 18th and 19th century forts and batteries. Portsmouth's defences began around the harbour, the large expanse of shallow, sheltered water spreading out behind the coastline and below Portsdown Hill. From here a defensive network which eventually included both land and sea forts, batteries, bastions and defensive lines spread to eventually include the Solent from the Needles Passage to Spithead and, on land, Portsdown Hill. Within this network, individual fortifications such as Fort Cumberland, the last self-contained, fully bastioned fortress to be built in England, are of considerable importance. Little altered from its original condition, Fort Cumberland is one of the most impressive pieces of 18th century defensive architecture remaining in England.

Legacy Record - This information may be included in the List Entry Details.

The monument includes Fort Cumberland, a large late 18th century angled bastioned fort lying on Portsea Island, a narrow spit of land on the west side of the channel leading into Langstone Harbour. The fort, which lies on the site of an earlier example dating from the mid- 18th century, is a regular star shape with five bastions and a ravelin on its western side. The interior contains a number of free-standing buildings, including officers' quarters, a hospital, stores and workshops, the majority dating from the use of the fort in the 19th and 20th centuries. The defences supported the main armament of the fort. Stone-faced with a brick parapet, the earthworks cover casemates, located mainly on the western side of the fort, which initially provided the majority of its accommodation. Four of the five lengths of curtain have central gates and the fifth, the Land Curtain, is now pierced by a modern vehicle entrance. The flanks of the five bastions have embrasures to provide enfilading fire along the curtains. Beyond the ramparts on all but the western (landward) side is a dry ditch, the outer face of which is brick-lined, rising up to a covered way which incorporates places of arms and traverses. The entrance in the left (seaward) curtain is approached by a road which crosses a place of arms and the ditch. The defences for this entrance were later strengthened by the construction of Pivot Battery housing a 10 inch RML gun. On the western side of the fort is a ravelin designed to cover approaches from the landward side. Beyond both ditch and ravelin is a glacis which survives only partly, having been damaged by the construction of water treatment works on the east side of the fort. On the southern, seaward side within the area of Fraser Battery the glacis has, in places, been disturbed by later military building although parts of it will survive as a buried feature beneath levelling-up deposits. To the south of the ravelin a high angle fire battery was inserted into the glacis in the 1890s, necessitating the construction of an access tunnel from the ditch. To the west and north west of the ravelin the profile of the glacis has been restored after episodes of minor disturbance. The first fort on the site, named after the Duke of Cumberland, was constructed around 1747 in the form of an irregular pentagon with two principal bastions, facing south and east. Little of this first fort remains although the guardhouse and storeroom survive, the latter with 19th century additions. The second fort, which remains largely intact, was built between 1785 and 1812 on the same site but to a different and larger plan. During the 1860s additional accommodation was added and in the 1890s the fort was modernised to take new breech loading guns on the left, south and centre bastions. The armament of the fort was again modified during the First and Second World Wars. A number of features within the area are excluded from the scheduling; these are all modern fence posts, security and custodial fittings and facilities, lighting, the surfaces of all paths, roads and areas of hard standing, military buildings within Fraser Battery and all free-standing buildings within the interior of the fort; the ground beneath all these features, is however, included. The monument is in the care of the Secretary of State and is Listed Grade II*.

MAP EXTRACT The site of the monument is shown on the attached map extract. It includes a 2 metre boundary around the archaeological features, considered to be essential for the monument's support and preservation.