The first, then still timber castle in Grosmont was probably built in the second half of the 11th century by the Norman conqueror William Fitz Osbern, Earl of Hereford. Shortly after William the Conqueror’s invasion of the island and the victorious battle of Hastings in 1066, he received border areas with Wales, where he erected castles in Chepstow and Monmouth, from which he undertook expeditions to further lands of central and eastern Monmouthshire. Grosmont was one of three wood-earth strongholds (the others were Skenfrith and White Castle) built at that time in the Monnow Valley to protect the route from Wales to Hereford and to control the conquered lands. It was built in an area whose population was entirely Welsh, which is why the rebellions and uprisings against Norman superiors caused it to be of great strategic importance for a long time.
William Fitz Osbern did not enjoy his Welsh lordship for too long, as he was killed in the Battle of Cassel in Flanders in 1071. William’s son, Roger de Breteuil, lost his castle because of his involvement in the rebellion against William the Conqueror in 1075. After a short period of possession by the Crown, Grosmont at the beginning of the 12th century became the property of the Anglo-Norman nobleman Pain fitz John, royal official of Henry I. When the English king died in 1135, there was a major Welsh revolt, which made king Stefan reorganize the landholdings along this section of the Marches, transferring the Grosmont castle and the nearby Skenfrith and White Castle fortifications back under the control of the Crown, to create an authority known as “Three Castles”. The conflict with the Welshmen continued, and after a period of detente under the rule of Henry II in the 60s of the twelfth century, the de Braose and Mortimer families resumed their expansion in the 70s. In 1182, the Welsh attacked the nearby Abergavenny Castle, which forced the king to strengthen the castle under the supervision of royal official Ralph of Grosmont. The small amounts spent on the work of that time suggest that the castle was still small and timber at the time.
In 1201, King John gave the “Three Castles” to Hubert de Burgh, a growing royal official, experienced in the fighting in France and familiar with the latest trends in military architecture. The new owner and then his son Hubert de Burgh II, by 1232 transformed the castle into a modern for the 13th century standards, stone building, which defense was based on flanking towers extended beyond the perimeter, but which also served as a residence. In 1227 the ruler Henry III gave Hubert 50 oaks from the royal forest for construction works, but in 1232, Hubert fell out of royal favors and was deprived of his possessions. The castle’s management was granted to king’s servant, Walerund Teutonicus. A year later, king Henry led the army to Wales against the rebellious Richard Marshall, Earl of Pembroke and his Welsh allies. He set up a camp at Grosmont, on which Richard carried out a night attack. He did not get the castle itself, but he forced the royal army to flee.
In 1234, Hubert reconciled with the king. The castles were returned to him, but in 1239 he again fell into conflict with Henry III. Grosmont was taken away from him and put under the command of Walerund. He did some of Hubert’s work, including the construction of a new chapel. In 1254 Grosmont and his sister strongholds were granted to the eldest son of king Henry, and later to king Edward. In 1262 the castle was prepared for a siege in response to the attack of Llywelyn ap Gruffudd on Abergavenny. Gilbert Talbot was ordered to be garrisoned “by every man, and at whatever cost”, but Grosmont missed the threat.
In 1267, Edmund, Earl of Lancaster and capitaneus of the royal forces in Wales received the Three Castles. The conquest of Wales by Edward I in 1282 caused the lowering of military importance of Grosmont, but in the first half of the fourteenth century, under the rule of Henry Lancaster or his son Henry of Grosmont, the interior of the castle has been modernized in high-quality apartments.
The last military episode in the history of the castle was Owain Glyndŵr’s revolt at the beginning of the 15th century. In 1404, a battle took place between the Welshmen and the victorious Richard Beauchamp, the Earl of Warwick, under the walls of the Grosmont, leading to an English victory. The following year, the castle was besieged by Owain’s son, Gruffudd, but it was relieved by the by prince Henry.
In 1538 the Grosmont castle ceased to be used, and then fell into ruin. In 1563 the bridge to the castle was already collapsed and although the external walls were intact, the interior was in a state of decay. The wooden parts rotted and the iron and lead elements were taken away.
The original castle from the 11th century was built of earth and wood in the form of motte and bailey. Probably it was either a timber keep placed on an earth mound, or protected by a palisade and a ditch defensive circuit (ringwork). It was situated on a vast elevation of land, the slopes of which fell to the east towards the bend of the Monnow River, but it was located on the outer side, not the inner side of the river meander. A little farther to the south, the castle was surrounded by the Tresenny Brook flowing south-east into Monnow.
The castle in its final form consisted of the upper ward and the outer bailey, which is invisible today. The oldest stone element of the upper ward was a rectangular residential range measuring 29 by 9.8 meters, from the beginning of the 13th century, which was located in the eastern part of the courtyard. Its massive walls were 2.2 meters thick, were reinforced with a battered plinth securing the building from the side of the slopes of the ditch, and also received three external façades reinforced with pilaster buttresses (also located in places where there were fireplaces inside). On the first floor in the northern part there was a private chamber (solar), and further on in the south most of the floor was occupied by a great hall, accessible from the courtyard through wooden stairs. The ground floor housed the pantry and the kitchen to which two western portals led, with doors closed from the inside with drawbars, placed in the holes in the wall. The lighting of the lower floor was provided by eleven small, narrow slit windows. In the kitchen, which occupied the southern part of the ground floor, there was a fireplace with a chimney towering over the central part of the southern wall. The upper hall was accessed via the mentioned external stairs, but the servants could also get to the upper floor using a spiral staircase located in the wall thickness in the southeast corner. Both the great hall and the private chamber had fireplaces, and both rooms were well lit with larger windows than below, additionally equipped with seats from the side of internal niches. In the great hall meals were eaten, feasts were organized and guests were invited, while the northern chamber was a private room and probably a bedroom.
The southern entrance gate to the castle and the west, polygonal defensive wall reinforced with towers were built in the 20s of the 13th century. The gate was placed in a two-story building of dimensions 13.3 x 8.2 meters with rounded corners, protruding beyond the perimeter of the walls. Inside, there was a gateway below, and a room for the guards above the wooden ceiling. At the bottom there were also two portals pierced on both sides of the building. North-east led to a narrow, flat platform between the wall and the moat, and the second to the upper floor. In the fourteenth century, the gate received an additional foregate, protecting a wooden drawbridge, erected over a moat and a pit formed between the walls of the foregate.
Two towers on the west side and one on the north side had a horseshoe shape with an outer diameter of approximately 8 meters and protruded beyond the perimeter of the walls enabling side fire. All, apart from three above-ground floors, were also equipped with round basements, accessible through openings in the ground floor and able to contain significant amounts of supply. This infrequent solution may have been a reflection of Hubert de Burgh’s experience of defending Chinon and Dover castles that have been subjected to prolonged sieges. In the fourteenth century, the western towers were raised and crowned with battlements instead of earlier hoarding. Their two upper floors were equipped than with chambers heated with fireplaces. A portal, accessible after a few stairs from the level of the courtyard, led to the south-west tower, enlarged from the side of the courtyard by a 2.5-meter wide part, in which a spiral staircase to the upper floors was immediately on the right of the entry. These upper floors were also accessible via wooden stairs attached to the inner face of the perimeter wall between the western towers. Their construction was based on two stone pillars.
In the fourteenth century, the northern tower along with the postern gate next to it were transformed, and ground floor of the tower was incorporated into the northern range, formed with a characteristic octagonal, gothic chimney from the courtyard side. This building had three floors with comfortable chambers heated by fireplaces. Next to it, on the west side, a new, rectangular tower was erected entirely in front of the face of the walls, probably to reward the loss of an older horseshoe tower. Inside, among others, there was a latrine and an unlit basement. The remaining buildings of the castle were timber, smaller houses erected at the courtyard at the inner faces of the defensive walls. In the fourteenth century or at the end of the Middle Ages, some of them were demolished, and some were replaced by stone ones. At the time, the building on the west side of the gatehouse probably housed service and garrison quarters. At the outer ward there was a rectangular granary or stable.
The castle has survived to modern times in the form of a ruin. Most of the defensive walls have survived, two western towers and the outer walls of the main building on the eastern side. In a much worse condition there is an entrance gatehouse and a four-sided tower, from the north range only a chimney and a part of the wall from the side of the inner ward remained. The moat around the castle is visible. The monument is under government protection and open to the public.
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Knight J., The Three Castles: Grosmont Castle, Skenfrith Castle, White Castle, Cardiff 2009.
Lindsay E., The castles of Wales, London 1998.
Salter M., The castles of Gwent, Glamorgan & Gower, Malvern 2002.