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