Skenfrith Castle Skenfrith Castle ( ) is a medieval castle located in Monmouthshire , Wales . The castle is in the centre of the village of Skenfrith , located on the banks of the River Monnow , five and a half miles north - west of the town of Monmouth . The first defences were built shortly after the Norman Conquest of 1066 , although the remains of the castle that stand today date from the early thirteenth century . The castle is a Grade II * listed building as at 19 November 1953 . Grouped with White Castle and Grosmont Castle , Skenfrith is one of the " Three Castles " or Trilateral Castles built in the Monnow Valley as part of the Norman conquest of South Wales . History of " The Three Castles " . 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 east , 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 1130s 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 Castle between 1219 and 1223 and Grosmont Castle 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 favour 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 1260s 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 . Although the Three Castles briefly saw action during the rebellion of Owain Glyndŵr in 1404 - 05 , they never again played a major role in military affairs . Henry VI carried out repairs to White Castle and Skenfrith Castle in the mid fifteenth century , but by 1538 the castles were abandoned , and ruinous . In 1825 the duchy of Lancaster sold the castles to the duke of Beaufort , whose estate divided them and sold each to different local landowners in 1902 . White Castle was given to the State in 1922 , followed by Grosmont in 1923 . Skenfrith passed through several hands before being given to the National Trust . All three castles are now conserved and maintained by Cadw , and are open to the public . Building of Skenfrith Castle . The remains of the castle as it stands today date entirely from Hubert de Burgh ' s work , when he totally rebuilt the castle between 1219 – 23 . Excavation has shown that the castle sits on an artificial gravel platform , up to twelve - feet thick . Evidence suggests that a defensive ditch would have surrounded the site , with timber walls . This early castle probably dates back to just after the Norman Conquest . Ralph of Grosmont is recorded as having spent 43 pounds on Skenfrith Castle in the Pipe Roll of 1186 – 87 . In the same excavation that discovered the early Norman defensive ditch , a twelfth - century stone wall was found , which suggests that Ralph was building in stone . A well carved decorative capital of red sandstone from the same period suggests a building of high quality , possibly a keep or hall . The location of the stonework , close to the early earthen defences of the castle , suggests that a such a keep or hall would have stood alongside the perimeter of the castle , just as is the case of the hall at Grosmont castle , which was built in the same period . Hubert de Burgh leveled these early defences , and no visible trace of them can be found . His new castle was built in the style of a concentric castle ( which was quite cutting - edge for the time ) , albeit on a very modest scale . The castle consisted of a round keep with three floors , surrounded by a curtain wall with a round tower at each corner . Around the wall would have been a moat with a stone revetment , as seen at White Castle . The moat was filled with water from a connection to the River Monnow , which passes just to the eastern side of the castle . The entrance to the castle was in the northern wall – today it is simply a gap , but an engraving by the Buck brothers in 1732 shows the remains of a simple arch of stone in the center of the wall . Along the eastern wall a flight of steps leads down to a lower archway which probably served as a water gate , giving access to the moat . Next to the south - east corner tower is a blocked archway which may have been a postern gate to the rear of the castle . The curtain walls have a sloping batter ( the wall slopes down to be thicker at the base than along the top ) for extra defence , and would have included a wall walk all the way around the inner edge . Support holes in the curtain wall , just below the level of the wall walk , were to support a timber hourding , or fighting gallery , which projected out from the wall and protected the defenders atop the wall . Each corner tower was built with a solid circular basement , presumably accessed by a wooden ladder from the upper levels . The towers would have been entered on the first floor via a wooden staircase from the outside . There were no windows , just arrowslit s , suggesting that the towers were purely for defence , not residence . Within the bailey there was a two - story hall block running along the inside of the western wall . The ground level was filled in with gravel in the thirteenth or fourteenth century , when the level of the castle ' s interior was raised in an effort to combat winter flooding . A later room was added along the northern wall , forming these buildings into an ' L ' shaped block . Given this room ' s size and east - west orientation , this may have been the castle chapel . The upper floor was divided into three rooms , and the fine quality fireplaces and stonework suggests domestic apartments , and possibly a Great Hall . On the southern end of this block of buildings was a square tank which was the castle reservoir . Across the bailey , along the eastern wall between the south - east tower and the water gate would have been the kitchens . The lightly built foundations suggest that the buildings were timber , built up against the curtain wall , with stone fireplaces , hearths , and ovens . The main residence for the lord of the castle would have been in the round tower - keep which sits at the middle of the inner bailey . Entrance to the keep would have been , like the corner towers , through a doorway above the ground level , reached by a wooden stairway from the bailey . The bottom level is again a basement , while the upper two floors would have contained apartments . A turret projects from the western side of the keep , this would have held the spiral staircase that gave access to the upper levels . The well - appointed apartments included large windows , hooded fireplaces , and a private latrine . The keep was topped by a circular wooden hourding , similar to the one that surmounted the curtain wall . Very little alteration has been made to the castle over the centuries . The level of the castle was raised , as was mentioned earlier , and at some point earth was piled around the bottom of the keep , giving it the impression of being set atop a mound . A door was also cut into the keep at ground level , bypassing the first floor entrance . Along the western wall , an external tower was added . This tower is solid to the level of the wall walk , and was probably added in the thirteenth century . Visiting the Castle . Skenfrith is located on the B4521 , five miles north - west of Monmouth , and is an open site , which may be visited free of charge at any reasonable time of day . The moat has been filled in , and the castle is now surrounded by a grassy lawn in the centre of the small village of Skenfrith . Three of the four corner towers still stand , as does its curtain wall up to the level of the wall walk . The round keep is intact , and the foundations of the hall block along the western wall have been excavated as well . Skenfrith in media . Skenfrith Castle features in the 2010 " Doctor Who " episode " Amy ' s Choice " as a ruined castle in the fictional village of Leadworth .