Portchester Castle


Heritage Category:
Scheduled Monument
List Entry Number:
Date first listed:
Date of most recent amendment:


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The building or site itself may lie within the boundary of more than one authority.

Fareham (District Authority)
National Grid Reference:
SU 62446 04604

Reasons for Designation

Saxon Shore forts were heavily defended later Roman military installations located exclusively in south east England. They were all constructed during the third century AD, probably between c.AD 225 and AD 285. They were built to provide protection against the sea-borne Saxon raiders who began to threaten the coast towards the end of the second century AD, and all Saxon Shore forts are situated on or very close to river estuaries or on the coast, between the Wash and the Isle of Wight. Saxon Shore forts are also found on the coasts of France and Belgium. The most distinctive feature of Saxon Shore forts are their defences which comprised massive stone walls, normally backed by an inner earth mound, and wholly or partially surrounded by one or two ditches. Wall walks and parapets originally crowned all walls, and the straight walls of all sites were punctuated by corner and interval towers and/or projecting bastions. Unlike other Roman military sites there is a lack of standardisation among Saxon Shore forts in respect of size and design of component features, and they vary in shape from square to polygonal or oval. Recognition of this class of monument was partially due to the survival of a fourth century AD Roman manuscript, the Notitia Dignitatum, which is a handbook of the civil and military organisation of the Roman Empire. This lists nine forts which were commanded by an officer who bore the title 'Officer of the Saxon Shore of Britain' (COMES LITORIS SAXONICI PER BRITANNIAM). Saxon Shore forts are rare nationally with a limited distribution. As one of a small group of Roman military monuments which are important in representing army strategy and government policy, Saxon Shore forts are of particular significance to our understanding of the period and all examples are considered to be of national importance.

The Saxon shore fort at Portchester is a well preserved example of its class. The entire defensive circuit survives with very little later modification. Within and around the fort there is significant evidence for its later use. The tower keep castle is an outstanding and well known example which demonstrates in its fabric a complex history of use and modification, while the 10th century defensive burh and the 12th century priory give the site an unusual dimension in terms of the range of uses to which it was put. Excavations over the years have demonstrated the extent to which remains of all aspects of its use and development survive. Both the shore fort and castle are in the care of the Secretary of State and are open to the public.


The monument includes Portchester Castle, situated at the end of a low promontory on the northern shore of Portsmouth Harbour. Originally constructed as a shore fort in the late Roman period, Portchester was reused in the Saxon period for settlement and, in the later 10th century, as a defensive burh. In the late 11th century a tower keep castle was constructed within the shore fort walls and was to be used for various purposes until the early 19th century. The outer bailey of the castle also incorporated the remains of an early 12th century Augustinian priory of which the church of St Mary is the only part surviving above ground. The monument also includes the below ground remains of a Tudor storehouse within the outer bailey of the castle. The standing structures of the monument include the outer walls of the Roman fort which stand to a height of up to 6m, although the upper parts are medieval in date. The fort originally had four entrances, of which the main two, the Landgate on the northern side and the Watergate on the southern were substantially rebuilt at later periods. The fort also had 20 bastions, circular at the corners and semicircular at intervals along the sides. Twelve of the semicircular bastions together with those on the north west and south east corners survive. The walls of the fort are surrounded by two ditches. The inner lies immediately beyond the walls on the north, west and part of the south sides and reflects their alignment. Beyond this, and cutting off the end of the promontory to the north and west, is a more substantial curved ditch and inner bank. The inner and outer circuits are linked at a point adjacent to the south west corner of the fort. The Norman castle, with later alterations and additions, lies in the north west corner of the Roman fort and utilises part of its western and northern walls. The rectangular keep, originally single-storey, but later raised in height, is built across the Roman wall which was demolished along with its corner bastion. The remaining sides of the castle are defined by a curtain wall, incorporating a rectangular corner bastion and, on the southern side, a gatehouse. This extends into and over a wet moat filled tidally from the inner ditch of the Roman fort. The inner bailey of the castle is occupied by ranges of domestic buildings. The palace of Richard II forms the south and west ranges; the great hall to the south, and a range of apartments to the west. The Constables' House forms the north range and includes Ashton's Tower, added to its eastern end at a later date, while the east range was later converted into a substantial house. The Roman fort, one of a series built from the Wash to the Solent, was built in the late 3rd century AD, most probably after AD 260-8, and may be identified as the `Portus Adurni' named in a contemporary document. Excavations within the fort, primarily those carried out on behalf of the Society of Antiquaries between 1961 and 1979, have shown traces of timber buildings laid out beside a regular grid of streets and provided evidence of both civilian and military occupation up to the end of Roman Britain and beyond. The excavations have also shown evidence of settlement dating to the mid- fifth and to the seventh to ninth centuries AD. Sunken floored huts, timber houses and ancillary buildings were found, after which a break in occupation is marked by the extensive dumping of rubbish in the interior of the fort. In AD 904 Portchester was acquired by King Edward the Elder and became a defended burh. Within it excavations have shown buildings dating to the 10th and 11th centuries, including a large aisled hall, and a rectangular stone building around which a cemetery developed. The Watergate in the east wall was probably rebuilt before the Norman Conquest, with a gatehouse built in the southern half of the Roman opening. After the Norman Conquest the manor of Portchester was granted to William Mauduit and by the time of his death in about 1100 the inner bailey of the castle had been created. The raising of the keep to two storeys took place before 1120, at which date the castle reverted to the Crown. In about 1130 the castle was acquired by William Pont de l'Arche who may have built the curtain wall of the bailey. The doubling in height of the keep and the addition of a chapel and a chamber to its forebuilding must also have taken place at this time. Within the castle William founded a priory which was abandoned as unsuitable by 1150. By 1158 the castle had again reverted to the Crown and, in the late 12th century, domestic buildings began to appear around the inner bailey. The castle declined in importance during the 13th century; in a survey of 1275 the buildings were described as being old and ruinous. However, between 1320 and 1326 major building works were carried out with considerable expenditure on walls, gates and various halls and chambers. The buildings on the west of the inner bailey became a self contained palace, later rebuilt by Richard II in the years after 1396. The north east tower in the bailey, known as Ashton's Tower, was also built in the 14th century. These buildings marked the final stage of the military and domestic development of the castle after which the 15th century marked another period of decay. In 1527 a new store house was erected within the castle, but had been demolished and removed to Portsmouth by 1584. Sir Thomas Cornwallis made considerable alterations to the castle in the early 17th century after which it was used for housing prisoners of war on a number of occasions between 1665 and 1814. On the last occasion, during the Napoleonic War, barrack blocks were built in the outer bailey to house soldiers guarding the prisoners. After 1814 the castle was converted to a hospital, later being used as a prison for deserters and a store before finally closing in June 1819. The church and churchyard of St Mary's are totally excluded from the scheduling. All road surfaces, modern and other inhabited buildings,including number 219 Castle Street which is Listed Grade II, garden fittings, kerbs, light standards, seats, litter bins, wooden bridges and access structures, safety rails, grilles and all modern security, safety, custodial, marketing and sanitary fittings are excluded from the scheduling although the ground beneath these features is included. The castle, including the wall of the Roman fort, is Listed Grade I. The monument is in the care of the Secretary of State.

MAP EXTRACT The site of the monument is shown on the attached map extract.


The contents of this record have been generated from a legacy data system.

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Books and journals
Cunliffe, B W, Excavations at Porchester Castle III: Medieval, outer bailey etc, (1977)
Cunliffe, B W, Excavations at Porchester Castle III: Medieval, outer bailey etc, (1977)
Cunliffe, B W, Munby, J T, Excavations at Porchester Castle IV: Medieval, the inner bailey, (1985)
Cunliffe, B W, Excavations at Portchester Castle I: Roman, (1975)
Cunliffe, B W, Excavations at Portchester Castle II: Saxon, (1976)
Munby, J T, Portchester Castle, (1991)


This monument is scheduled under the Ancient Monuments and Archaeological Areas Act 1979 as amended as it appears to the Secretary of State to be of national importance. This entry is a copy, the original is held by the Department for Digital, Culture, Media and Sport.

End of official listing

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