History of "The Three Castles"
The term "The Three Castles" is used to collectively describe White Castle, Skenfrith Castle and Grosmont Castle, all of which are located in the Monnow Valley in south Wales.
The Monnow Valley was an important route between Hereford and Monmouth in medieval times, due to its position as an area of relatively open land, which provided a break between the river cliffs of the Wye Valley to the south, and the hills around Abergavenny to the west.
The Three Castles are usually grouped together by historians because for almost their entire history they were part of a block of territory under the control of a single lord.
All three sites have evidence for early Norman earthworks, possibly built by William fitz Osbern, who was made Earl of Hereford by William the Conqueror a few months after the Norman Conquest of England in 1066. From his castles at Monmouth and Chepstow, William was the first Norman lord to conquer central and eastern Monmouthshire, including the future sites for the Three Castles. The defences raised at this time would probably have been of earth and timber.
Fitz Osbern died in 1071, and his lands were forfeited to the crown after his son Roger de Breteuil was involved in a rebellion against King William in 1075. Later the king divided up this strategically important territory - the only time in their active history that the Three Castles were owned separately. They were reunited by King Stephen in the late 1130's as a response to Welsh rebellion in the southern March, and would remain a single lordship until the nineteenth century.
There is little evidence of building activity at any of the castles until the late twelfth century, when they were fortified by Ralph of Grosmont, a royal official who supervised building work for the king in Hereford. The castles were then completely overhauled by Hubert de Burgh, who was granted lordship of the Three Castles by King John in 1201. Control of the Three Castles was briefly granted to William de Braose in 1205, when Hubert was a prisoner of Philip Augustus, the king of France, but William quickly fell out of favour, and by 1207 John had forced him into ruin. Hubert de Burgh returned to power, and was appointed Justiciar in 1215.
From his time fighting in France Hubert had a knowledge of the latest in military architecture, and in the years after 1219 he was a prosperous lord who had great influence with King Henry III. He rebuilt Skenfrith between 1219 and 1223 and Grosmont between 1224 and 1226 in stone, adding domestic apartments to both castles, so that they could be used as lordly residences. He held the Three Castles until 1239, although they were briefly taken from him after he fell out of royal favor in 1232 (they were returned after his reconciliation to the king two years later).
After Hubert de Burgh, the Three Castles were held in royal hands, and in 1254 Henry III granted them to his eldest son, the future Edward I. In the 1260's the southern March was threatened by the Welsh Prince Llewelyn ap Gruffudd, who annexed the lordship of Brecon, and attacked nearby Abergavenny. Gilbert Talbot was appointed constable of the Three Castles, and ordered to garrison them 'at whatever cost'. Although Llewelyn's attack on Abergavenny failed, the Treaty of Montgomery in 1267 recognized his southern conquests, and he was considered a significant threat.
1267 saw the Three Castles being granted to Edward's younger brother Edmund, Earl of Lancaster. Although the Welsh threat was soon subdued with the death of Llywelyn in 1282, the Three Castles were used as residences and centres for local authority. The castles passed down through the earls of Lancaster until the death of Henry of Grosmont, Duke of Lancaster, whose daughter Blanche married John of Gaunt, son of Edward III. John of Gaunt was made Duke of Lancaster in 1364, and the Three Castles would remain part of the duchy of Lancaster until 1825. John and Blanche's son, Henry of Bolingbroke, deposed Richard II in 1399 and became King Henry IV, at which time the Three Castles also became royal possessions once more.