Possibly commissioned by William fitz Osbern, the Earl of Hereford, the castle comprised earthworks with timber defences.

Edward I's conquest of Wales in 1282 removed much of Skenfrith Castle's military utility, and by the 16th century it had fallen into disuse and ruin.

[2] The Normans used castles extensively to militarily subdue the Welsh, establish new settlements and exert their claims of lordship over the territories.

[3] Skenfrith Castle was one of a triangle of fortifications built in the Monnow valley around this time, possibly by Earl William himself, to protect the route from Wales to Hereford.

[4] The earldom's landholdings in the region were slowly broken up after William's son, Roger de Breteuil, rebelled against the King in 1075.

[5] In response, the Crown readied the castle to face an attack, and in 1186, £43[nb 1] was spent developing the defences followed by more work in 1190, probably establishing a stone keep and curtain wall.

[10] Once released, Hubert regained his grip on power, becoming the royal justiciar and being made the Earl of Kent, before finally recovering the Three Castles in 1219 during the reign of King Henry III.

[12] The Welsh threat persisted, and in 1262 the castle was readied in response to Prince Llywelyn ap Gruffudd's attack on Abergavenny in 1262; commanded by its constable Gilbert Talbot, Skenfrith was ordered to be garrisoned "by every man, and at whatever cost".

[14] King Edward I's conquest of Wales in 1282 had removed much of the castle's military utility, although it continued to be used as an administrative centre.

[16] It was eventually acquired by the lawyer Harold Sands, who carried out some conservation of the site; he went on to give the castle to the National Trust.

[17] In the 21st century, Skenfirth Castle is managed by Cadw and protected under UK law as a grade II* listed building.

[19] The curtain wall survives to a height of up to 5 metres (16 ft 5 in), and was probably originally topped by a 6-foot-high (1.8 m) parapet and protective timber hoarding.