PORTUS ADURNI (Portchester) Hampshire, England.
The castle stands on a low promontory projecting into the upper reaches of Portsmouth harbor. Limited occupation of the mid-1st c. A.D. has been found, but the main phase of use began in the late 3d c. with the construction of the Saxon Shore Fort. Excavations show that occupation continued throughout the Saxon period. In mediaeval times the Roman walls served as an outer bailey for a castle which, after a series of modifications, was eventually used as a prison during the wars between Britain and France in the late 18th and early 19th c.The Roman fort consists of a regularly planned rectangle enclosing ca. 3.6 ha. The walls were built of coursed flint rubble with the occasional use of chalk blocks, and with bonding courses of stone and tiles at intervals. Originally 20 hollow D-shaped bastions projected from the wall, one at each corner and four regularly spaced along each side. They were floored with timber at the level of the rampart walk to form fighting platforms for men and artillery. The two main gates were in the centers of the E and W sides. In both the full width of the wall was turned into the fort, creating a courtyard, at the inner end of which the gate was erected (two guard chambers flanking a 3.3 m roadway). Simple postern gates, 3 m wide, pierced the centers of the N and S walls. Outside, enclosing the fort, were two V-shaped ditches.
Extensive excavations began in 1961 in the enclosed area. Buildings were of timber, arranged along graveled streets; between them were cesspits and wells. Several phases of occupation can be defined. The first represents the use of the fort under Carausius and Allectus (A.D. 285-296), during which time Britain was self-governed and the shore forts were probably defenses against the threat of Roman attack. After the reconquest of Britain by Constantius Chlorus in 296 the garrison at Portchester was removed and some, at least, of the internal buildings were deliberately demolished, but the interior continued to be occupied by civilians. Early in the 340s renewed building activity can be recognized. It was probably at this time that the fort was regarrisoned, perhaps by the Numerus exploratorum listed in the Notitia Dignitatum. Intensive occupation ended about 370 during the reorganization carried out by Count Theodosius; the force may have been transferred to Clausentum, but occupation of a less organized kind continued into the Saxon period. Several sunken huts (Grubenhäuser) of Germanic type have been found, dating from the early 5th c.; they suggest the presence of mercenaries among the population of late Roman times.
The walls of the fort and the foundations of part of the W gate can be seen, but no interior features are visible. While excavations are proceeding the excavated material is not on display.
BIBLIOGRAPHY
B. Cunliffe, “Excavations at Portchester Castle, Hants, 1961-63,” AntJ 43 (1963) 218-27; “1963-65,” 46 (1966) 39-49; “1966-68,” 49 (1969) 62-74; id., “The Saxon Culture-sequence at Portchester Castle,” ibid. 50 (1970) 67-85.B. W. CUNLIFFE