Gatehouse and part of curtain wall of early C14 castle built for Aymer de Valence, Earl of Pembroke, who obtained licence to crenellate 1315. Adapted to dwelling C17, with mid-late C19 extension. Coursed limestone rubble, part ashlar, with stone slate roofs and ashlar chimneys. Gatehouse lies on east-west axis with contemporary lodging bay adjacent to north and C19-C20 extension in north-west angle. Running south from gatehouse is short length of curtain wall which masks larger C19 extension on east side. Forms house of 2 storeys and attic. Gatehouse has large archways with moulded labels, infilled with rubble and ashlar late C17. Infill is pierced by stone mullion windows, those to first floor late C17, of 3 lights, with ovolo mouldings. Similar 4-light window with Tudor hoodmould to ground floor on east side; C19 matching 3-light window with hollow chamfers on west side. West side of gatehouse projects, and has chamfered plinth, C14 flanking set-back buttresses, and C17 gable with 3-light leaded casement. Immediately above arch on west side is a horizontal slit with sloping ducts, possibly for drawbridge cables. East side has octagonal stair turret projecting to left, with battlemented parapet, trefoil-headed slit windows, and octagonal pyramid roof with weathervane. To right is C14 bay with contemporary 2-light traceried window to first floor. This window has arched head with label, cusped ogee tracery, and hollow mouldings. Below are a C19 3-light stone mullion window and a C19 half-glazed door. 2 gabled roof dormer; with 2-light casements. Curtain wall has chamfered plinth, wide battlements with slated coping, and 2 bays of cross slits. Upper right part of wall reconstructed C19. Behind is C19 extension, of 2 storeys, with first floor band course, coped gables and stone mullion windows with Tudor hoodmoulds. South side has large canted bay window to left; north side has porch with door in Caernarvon arch. C19 and C20 lean-to extensions at north end of house are small and have tiled roofs. Interior: gatehouse arches are moulded, the east arch of 2 orders, the west with one moulded order and rebates for gates. Side walls of east bay of gatehouse have small arched doorways with similar mouldings. Gatehouse also retains fine 2-bay vault with chamfered ribs and carved bosses, and stone spiral staircase to attic. First floor of C14 lodging bay has original fireplace with moulded stone jambs and stone hood on moulded brackets. Heavy stop-chamfered ceiling beams. C17 fireplace inserted to first floor of gatehouse, with chamfered stone arch. (Listed Building Report)
The castle, later Ham Court, was built on the town's western edge by Aymer de Valence c. 1315, in which year he received a licence to crenellate. It remained the manor house for Bampton Earls manor, and was divided between the two moieties from the 17th century until 1871. A 13th-century window surviving in 1821 suggests that the castle succeeded a house built by Aymer's father William c. 1256, when he received oaks and beams for his new hall, and presumably there was an earlier royal manor house on or near the site: wine was sent to Bampton as well as to the royal palace at Woodstock in 1210, and letters close and patent were dated from Bampton in 1236 and later. The castle was partly ruined by 1664 and was mostly demolished before 1789; surviving remains, all of c. 1315, comprise the lower half of the west gatehouse, abutted on the north by a rectangular lodging range of 2 storeys, and on the south by c. 10 m. of curtain wall. Before 1660 the gatehouse and lodging range were converted into a farmhouse, called Ham Court presumably from nearby Ham field, and further alterations were made in the 18th and 19th centuries. It remained a farmhouse in 1994.
A drawing of the west front in 1664 shows the gatehouse crenellated, with, over the gate passage, a tall, two-light transomed window, presumably with curvilinear tracery similar to that in the northern lodging range. The gatehouse formed the centrepiece of a symmetrical front of 4 bays, which extended north and south to round corner-towers with 3 tiers of arrowslits, and which had 2 intermediate projecting turrets supported on pillars 'partly ... within the wall, and partly standing without'. The castle was said to be quadrangular, with round towers at each corner and similar gatehouses on the east and, possibly, north and south, implying a symmetrical plan grouped around a courtyard. A projection based on surviving remains, corroborated by earthworks to the west and north and by watercourses to the east and west, suggests a frontage of c. 110 m. (360 ft.), far larger than Aymer's castle at Goodrich (Herefs.), which may indicate that Bampton castle was planned as the caput for his barony. Surviving ditches and a residual scarp to the west suggest a broad moat c. 30 m. wide.
The gatehouse, projecting forward from the line of the curtain wall, retains pairs of angle buttresses on the external corners, with scars for similar buttresses on the east. Small embrasures for arrow-slits survive in the side walls at the west end of the gate passage, and at the east end are a pair of two-centred doorways, the northern leading to the ground floor of the lodging range, and the southern to a polygonal stair turret with tiny cusped-headed single-light windows, which rises to the level of the demolished upper chamber over the gate passage. Internally the gate passage comprises two square, rib-vaulted bays, each with a much-damaged foliage boss. The lodging block's upper storey retains a fireplace of high quality with moulded jambs and a corbelled stone hood, and in the east wall a two-light transomed window with curvilinear tracery. Its ground floor has no medieval features, and its north end has been truncated or rebuilt.
Despite its size, the castle seems to have been used only as an occasional residence. Aymer stayed at Bampton in 1307 and 1312 but is not known to have visited after 1315, and Gilbert, Lord Talbot (d. 1387), leasing the manor to Sir Robert Tresilian in 1382, reserved the right to stay for a day and night if the lessee and his wife were absent. Other parts of the castle and its associated buildings may already have been derelict, since in 1422 the remaining two-thirds of the manor included a stone house with granges and other 'ruined' buildings. Some bailiffs in the 15th century may have been accommodated in the castle, and by the later 16th century the whole site, variously described as the castle or mansion house or as Ham Court, was let with the demesne to the lord's steward or to local gentry, some of whom probably sublet it. In the earlier 17th century the demesne and some agricultural buildings were sometimes let separately. (VCH)