Llanthony Priory () is a partly ruined former Augustinian priory in the secluded Vale of Ewyas, a steep-sided once-glaciated valley within the Black Mountains area of the Brecon Beacons National Park in Monmouthshire, south east Wales. It lies seven miles north of Abergavenny on an old road to Hay-on-Wye at Llanthony. The priory ruins lie to the west of the prominent Hatterrall Ridge, a limb of the Black mountains. The main ruins are under the care of Cadw and entrance is free. The priory is a Grade I listed building as of 1 September 1956. Within the precincts of the Priory are three other buildings with Grade I listed status: the Abbey Hotel, listed on 1 September 1956; St David's Church, listed on the same date, and Court Farm Barn, listed on 9 January in the same year. History Foundation The priory dates back to around the year 1100, when one of Hugh de Lacy's knights called William reputedly came upon a ruined chapel of St. David in this location, and was inspired to devote himself to solitary prayer and study. He was joined by Ersinius, a former Chaplain to Queen Matilda, the wife of King Henry I, and then a band of followers. A church was built on the site, dedicated to St John the Baptist, and consecrated in 1108. By 1118, a group of around 40 canons founded there a priory of Canons Regular, the first in Wales. In 1135, after persistent attacks from the local Welsh population, the monks retreated to Gloucester where they founded a secondary cell, Llanthony Secunda. However, around 1186 another member of the de Lacy family, Hugh, the fifth baron, endowed the estate with funds from his Irish estates to rebuild the priory church, and this work was completed by 1217. There are also letters from Pope Clement III (CSM,i,p. 157–159), between 1185 and 1188, confirming further grants and gifts to the priory from Adam de Feypo and Geoffrey de Cusack in Ireland. The Priory became one of the great medieval buildings in Wales, in a mixture of Norman and Gothic architectural styles. Renewed building took place around 1325, with a new gatehouse. On Palm Sunday, April 4, 1327, the deposed Edward II stayed at the Priory on his way from Kenilworth Castle to Berkeley Castle, where he is alleged to have been murdered. Dissolution Following Owain Glyndŵr's rebellion in the early 15th