granted to King Henry's eldest son, and later king, Prince Edward. 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". The threat passed without incident. Edmund, the Earl of Lancaster and the capitaneus of the royal forces in Wales, was given the Three Castles in 1267 and for many centuries they were held by the earldom, later duchy, of Lancaster. Little further work was carried out at Skenfrith, although repairs were carried out to the tower and gates under King Henry VI. 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. By 1538, Skenfrith Castle had fallen into disuse and then into ruin; a 1613 description noted that it was "ruynous and decayed". 18th–21st centuries In 1825, the Three Castles were sold off to Henry Somerset, the Duke of Beaufort. 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. Skenfrith was placed into the care of the state in 1936, and extensive repair work was carried out. In the 21st century, Skenfirth Castle is managed by Cadw and protected under UK law as a grade II* listed building. Architecture Skenfrith Castle was constructed alongside the River Monnow. The current castle was created by Hubert de Burgh in the early 13th century, when the earthworks of the 11th-century Norman castle were flattened and spread out over the current site to a depth of ; the 12th-century stone fortifications and buildings were demolished at the same time. Hubert's castle forms a polygon, with four walls approximately 80 metres, 60 metres, 60 metres and 40 metres (260 ft, 200 ft, 200 ft and 130 ft) long respectively, and was built from Old Red Sandstone. It was originally protected by a stone-revetted, water-filled moat, deep and wide, fed by the river. The moat is now filled in and grassed over. The castle was entered from the north-west side over a bridge and through a gatehouse, both since destroyed. The curtain wall survives to a height of up to , and was probably originally topped by