Castle, now prison and courthouses. Occupies part of the site of a Roman fort. Principal dates of construction of the surviving structure are c1150, when the keep was erected; c1200 (parts of Hadrian's Tower, fragments of curtain wall running north and east from the tower, some masonry in the Gatehouse passageway, and the lower part of the Well Tower); early C15 (the Gatehouse and Well Tower). The upper storey of the keep is probably C15 and was re-modelled in 1585. Extensive additions were made from 1788 onwards to the designs of Thomas Harrison. The Governor's house was the first of the new buildings. The former Crown Hall at the west was rebuilt and extended to the north to include a new Crown Court (1798) and circular Grand Jury Room. To the west a new Shire Hall was built on a 7-sided semicircular plan. The female felons' prison was completed in 1793, and the male felons' prison to the north was also built in the 1790s. Following a break, work continued under the supervision of JM Gandy in 1802: the interior of the Crown Court was completed, and the female penitentiary was added in 1818-21. The walls are of sandstone ashlar and rubble with roofs of slate and lead. All the buildings are linked to form an irregular polygon on plan with a central courtyard. The Gatehouse, of 3 storeys and with 2 towers which have projections of semi-octagonal plan, linked by a passageway arch which dies into the reveals, and have machicolations and embattled parapets. To each side square turrets, with taller stair turrets, rise above the parapets. Above the gateway a niche contains a statue of John O'Gaunt by Claud Nimmo, installed in 1822, flanked by shields of arms of Henry V when Prince of Wales (1407 - 1413). The former female penitentiary on the south side of the courtyard is linked to the gatehouse by the former female felons' prison. Of 5 storeys and semicircular plan with its curved wall facing a small yard formed by the curtain wall to the south. The interior contains cells, 9 to each floor, radiating from landings with cast-iron stairs. Within the yard the wall extending from the cell block towards the west contains rubble masonry from the curtain wall of c1200. This forms the south wall of the former debtors' rooms, added by Harrison, a range of buildings which is continued towards the north where it abuts the parallel Crown Court range, and returns towards the east against the south wall of the keep. The north-south range, which forms the west side of the courtyard, has cantilevered stone staircases at each end. The keep is of 4 storeys. The east wall contains the blocked round-arched first-floor entrance doorway and now has a 3-light mullioned and transomed window. On the ground floor are 2 doorways with pointed wave-moulded arches. Some round-headed window openings with angle shafts remain, including 2 at first-floor level in the north wall. On the north side the battlements have a plaque inscribed 'ER RA 1585'. Internally, the tower is divided into 2 compartments by a spine wall. At ground-floor level 2 of the massive timber posts which support the first floor are visible in the southern half. The former Male Felons' prison, to the north, built on a radial plan with 2 cell blocks of 5 storeys linked by a rebuilt curtain wall. The western block has been altered by the addition of a late C19 range of cells. Between this block and the Keep is the former Execution Yard, with a blocked 'Hanging Doorway' in the curtain wall. The eastern cell block is relatively unaltered and used for storage, with each floor having 2 groups of 4 cells, separated by a spine wall and served by 2 landings. The original cast-iron doors remain. The Well Tower on the west side of the courtyard is of rectangular plan with a long flight of stone steps leading down to a cellar. To the north of the steps a niche contains a well. The stonework of the pointed cellar vault has mortar which retains the impression of the wattle centering used in its construction. The former GOVERNOR'S HOUSE, to the south, has the centre of its facade canted forwards and has Gothick windows. At the west of the complex are the courtrooms and associated buildings. The Crown Court range was built partly on the site of the earlier Crown Hall and has semicircular north and south terminations: to the south is the re-cased Hadrian's Tower and to the north the new Grand Jury Room. Projecting on the west side is the Shire Hall, with a ground-floor arcade of Tudor arches, with a walkway above, and with pointed windows lighting the Hall itself. All the openings have Perpendicular tracery. INTERIORS. Gatehouse: the upper rooms of the towers contain cambered roof beams carried on corbelled wall posts. A corridor above the entrance passage contains the following graffito incised into the stone: 'John Bailey Committed April ye 15th, 1741 by Brindle, for kissing', together with a drawing of a fiddle. Inside the Shire Hall an elliptical arch spans the full width of the courtroom, its wide soffit decorated with blind tracery plasterwork. Below, the east wall contains 3 pointed windows above a continuous Gothick plasterwork canopy, added by Gandy. In front of the arch the ribs of the ceiling vault radiate from a central boss and spring from 7 clustered sandstone columns which form an ambulatory around the outside wall. To each side of the judge's seat are jury boxes, and benches are arranged in a segmental pattern: the woodwork is in a Gothic style and was supplied by Gillows. The Crown Court was decorated by Gandy and has Gothic woodwork which includes a canopy over the judge's chair. The Grand Jury Room is vaulted and has curved Gothic doors. Hadrian's Tower now has exposed stonework internally, squared below and of rubble above. The circular gallery was added in 1892 when the tower was excavated to its present level. At gallery level is a blocked round-arched opening of c1200. To the north of Hadrian's Tower there is a barrel-vaulted corridor under the site of the old hall. Opening off it are 5 barrel-vaulted cells with timber doors, possibly used originally as stables but in use as prison cells by the C18. (Listed Building Report)
It has been presumed the Masonry castle occupies the site of an earlier castle of motte and bailey form. It is also said the great tower is built on a mound (dated as Saxon by Cox (1896) although his plan suggest he thought the whole castle was built on a large mound overlying the corner of a Roman fort). The presumption their was an earlier timber castle here is probably correct. The evidence this was of a motte and bailey form is less good and seems mainly to be made by an assumption that all Norman castles were of this form. The layout of the castle suggests to Gatehouse
that the original timber castle was initially a ringwork without a motte but if this was a motte it was a large and low mound. According to Goodall (2013) the timber castle was started in 1094 and the Lungess tower soon after 1102. Eight years is far too short a period of time for an artificial motte to stabilise so the great tower cannot be built on a motte on the tall conical form.