Newcastle Castle is a relatively large but little known Norman fortification in the centre of Bridgend, constructed atop a low ridge on the west side of the Ogmore River, overlooking an ancient crossing point, and was established by the comparatively early date of 1106. Half a mile southeast, on the opposite bank of the river is the district of Oldcastle, the origin of which is uncertain, but it is likely that an earlier castle once stood here, though an alternative theory holds that the Bridgend's 'Oldcastle' was actually Coity Castle, beyond the east edge of the town.
Nearly all the visible masonry at Newcastle Castle is from late 12th century - a gateway and adjacent tower, still partly three stories high, and a complete curtain wall incorporating the base of a second tower, while inside the protected area are foundations of three other rooms, one possibly an earlier keep. The castle was occupied until the late 16th century, when the gateway tower was converted to a residence, but has been ruinous for over 300 years.
The north and east sides of the castle have natural protection afforded by steep slopes, partly wooded, while to the west, the exterior of the curtain wall now forms the boundary of the gardens of a row of modern houses. Access is from the south, from an outer grassy area behind a wall and gate that is unlocked during daylight hours. The site is free to access and open all but three days of the year. Vehicles can be parked right outside along a short street (The Square), off Newcastle Hill. The site lies very close to the main road into Bridgend from the north (A4063), though is reached via quiet residential lanes, and is not obviously signposted.
The first fortification on the site was a simple ringwork castle; a courtyard enclosed by a timber fence, possibly augmented a few decades later by a small stone keep at the centre. The castle was built by Glamorgan knight William de Londres, an associate of Robert FitzHamon, the Norman conqueror of Glamorgan, and upon his death, the castle passed first to his daughter Mabel and then to her son William FitzRobert, 2nd Earl of Gloucester, and it was he who began the process of rebuilding the castle in stone, the structure seen today. The work was completed by Henry II following William's death in 1187, soon after which ownership changed several times in quick succession until the castle was acquired by the de Turberville family, in whose keeping it remained for several centuries, though they mostly resided at another of their properties, nearby Coity Castle. After this it was sold a few more times before gradually becoming disused in the 17th century.
The castle entrance is in the middle of the south curtain wall, via a flight of (modern) steps through a fine, ornate doorway - the highlight of the site, beneath a segmented arch decorated by niched stones, on the outside of which is a wider, semicircular arch resting on ionic columns. All constructed of light grey Sutton stone, also used for the dressing of all angles and window frames, and surviving in most places. Just west of the doorway is the three-storey south, or gatehouse, tower, the ground floor of which is closed by a gate. This tower, like the incomplete west tower, is square in cross-section, reflecting its relatively early construction, as most later castles incorporated more easily defensible round towers. The impressive curtain wall, 500 feet in circumference, encloses a roughly circular courtyard which contains fragmentary foundations against the north wall and slightly higher remains to the southeast, of two buildings, one possibly the original keep. The perimeter wall is full height to the north and still substantial on the all sides; to the east it extends some distance below the inner ground level, reinforcing the natural rocky slope. The wall is built in straight sections, presumably as these were easier to build than smooth curves.