We know little about the early history of Anderida, the Roman fort at Pevensey. Tree-ring dating of wooden piles sunk into the wall foundations suggests that it was built in about AD 290. At that time the coastal defences of Roman Britain seem to have been systematically strengthened, and a number of other forts around the south and east coasts, such as Portchester, Burgh, Richborough and Lympne, were built or reconstructed.
After the withdrawal of Roman troops from Britain in the early 5th century, Anderida’s walls continued to shelter a community. The Anglo-Saxon Chronicle records that in 471 the fort was besieged and its population slaughtered by Saxon raiders. The fort was abandoned for around a century before it was inhabited again. Little is known about it in Anglo-Saxon period, though traces found by archaeologists such as fragments of glass suggest it was a high-status place. It may even have acted as a royal centre.
Pevensey’s history changed dramatically when, before dawn on 28 September 1066 – three days after King Harold’s victory at Stamford Bridge – William, Duke of Normandy, sailed his invading fleet of about 700 ships into the Bay of Pevensey. After landing, he immediately built a temporary fortification, almost certainly within the walls of the Roman fort, to shelter his troops. He cut a ditch across the peninsula to isolate the ruins from the mainland and repaired the walls to create a castle.
It is not known for certain when the stone buildings of Pevensey Castle’s Inner Ward were built but a series of regular payments by Richard I in the 1190s suggest substantial building activity at this time. It is possible the Great Keep was one of these buildings or, if it already existed, it was certainly substantially modified at this time. However, the castle was probably slighted by the forces of King John in 1216 during the First Barons’ War, when south-east England fell under the control of Prince Louis of France. The damage was repaired after the war and in 1230 the castle was granted to Gilbert Marshal, Earl of Pembroke. In 1246 it was given to Peter of Savoy who commissioned substantial upgrades to the site. This included halving the size of the Inner Bailey and replacing the former timber palisade with a stone wall. . . . The castle played no part in the Wars of the Roses and was allowed to fall into decay and ruin although its role as a regional prison continued. Inmates included a number of high status magnates including King James I of Scotland, who had been captured in 1406, and Henry IV’s widowed queen, Joan of Navarre. By the sixteenth century the castle itself was ruinous although in 1587, faced with the threat of a Spanish invasion, emergency repairs were made by Elizabeth I and a gun emplacement built within the Outer Bailey.
Castles Forts Battles
Layout of Pevensey Castle, from “The castles of England, their story and structure“, James Dixon Mackenzie, 1896 p.82
The Normans, who at once saw the value and took possession of Pevensey, probably were for a time content with the Roman walls as they stood, and with the palisaded citadel of the mound. At least, there is no certain trace of any very early Norman masonry. Indeed, the only masonry of Norman date at all now to be seen is a fragment of wall with a window, the remains of a superstructure upon one of the northern towers, and some patchwork in flints, and a few courses of stone laid herring-bone fashion, by which the face of another of the Roman towers has been repaired. Had the Normans of the eleventh or twelfth centuries constructed any eastern walls, gatehouses, or mural towers within the court, some trace of them would probably remain. The chapel, indeed, judging from its dimensions, was Norman, and the base of the font decidedly so; and it is possible that the shapeless fragments of rubble masonry which encumber the top and slopes of the mound may be of the same, that is, of late Norman, date. In truth, the castle, as the Normans found it, was a very strong place. The walls only needed a battlement, and even if this were surmounted, the entrenched and palisaded mound would be perfectly defensible so long as provisions held out.
Flanking the gatehouse, at a distance of 33 yards north and 54 yards south, are two grand round towers, each capping an angle of the curtain. The north curtain has a base or plinth slightly battering. The wall is vertical. There is no cordon between them. The north-west tower is 30 feet diameter, and has a basement, ground, and upper floor. The basement, though below the inner ward level, is on the level of the ground outside. It is arcaded, having six arches in its rounded sides, and one in its flat end or gorge. These arches have a drip of the double-scroll pattern, and between each pair springs a moulded rib, and one from each of the two right angles, eight in all. They are broken away, but their profile is seen, and the plan of the vault may be inferred. The entrance to this chamber is by a straight staircase from the inner366 ward, and at the foot of the stairs is a lobby on the left or west side leading to a postern doorway placed at the junction of the tower with the curtain. In the gorge wall is a fireplace, the hood of which seems to have been of timber. It is difficult to understand what this chamber can have been intended for, with its ornate details and a fireplace, and yet half under ground.
Mediæval Military Architecture in England, Vol. II“, George Thomas Clark, 1884