Monmouth Castle was built shortly after the Norman invasion and was intended to serve as a key fortress to check the power of the Welsh. It was later the birthplace of Henry V, victor of Agincourt, and during the seventeenth century Civil War it changed hands three times before it was slighted by Parliament. It remains an active military establishment today.



Monmouth Castle was built in the years immediately following the Norman invasion by William FitzOsbern. He was one of the key supporters of William I and had been instrumental in persuading the Norman Barons to support the invasion of England. In reward the King granted him the Earldom of Hereford which included extensive lands across the south-west Midlands. This also placed FitzOsbern in a position to secure the border region and, upon his own initiative, expand Norman control into Wales. He commenced construction of a series of fortifications to secure his new estates and Monmouth Castle was built to dominate the River Wye at the point of its confluence with the River Monnow. These key waterways were important logistical arteries that facilitated movement throughout the region and thus Monmouth was a key nodal point that enabled FitzOsbern to achieve effective domination of the region. Monmouth Castle was just one of several fortifications built along the southern stretch of the River Wye - Chepstow Castle, St Briavels Castle, Bicknor Castle and Goodrich Castle were all raised to secure this important waterway.


The castle was initially an earth and timber ringwork fortification. The oval shaped enclosure was protected by an earthwork rampart topped with a wooden palisade and fronted by a ditch on the east and south sides. The north and west was protected by steep natural scarp down to the River Monnow. The town, which was also protected by an earth and timber rampart, was laid out concurrently with the castle and a Priory established within the perimeter. Around 1150 the Keep was rebuilt in stone incorporating a Great Hall.


Monmouth Castle was briefly captured by Richard Marshal, Earl of Pembroke during his rebellion in 1233. It was perhaps this attack that prompted the then owner - John of Monmouth - to build the Great Round Keep circa-1236. In 1256 the castle passed into Royal ownership when it was acquired by Prince Edward (later Edward I). He held it until it was captured by Simon de Montfort in 1264 during his rebellion against Henry III. The King, whom Montfort had captured at the Battle of Lewes (1264), was briefly held at the castle as a prisoner. The rebellion was defeated the following year and the castle returned to the Crown. Henry III then granted it to his younger son, Edmund Crouchback, as part of a package of lands given to him when he was created Earl of Lancaster in 1267 (Grosmont, Skenfrith and White castles were also part of the gift). Edmund made numerous modifications to Monmouth Castle including adding an external Great Hall adjacent to the originally twelfth century Keep.


Following Edmund's death in 1296, Monmouth Castle and the Earldom of Lancaster passed to his son, Thomas. During his tenure the town defences were built in stone with the Crown granting him the right to collect tolls for this purpose between 1297 and 1315. Monnow bridge was probably constructed at this time. Thomas rebelled against Edward II and was executed in 1322 after which Monmouth Castle passed to his brother, Henry. He died in 1345 and Monmouth was then inherited by his son, Henry of Grosmont, Duke of Lancaster who remodelled the castle including the Keep. Henry died without leaving a male heir and in 1359 it passed to John of Gaunt through his marriage to Henry's daughter, Blanche of Lancaster. In 1387 John's grandson, Henry (later Henry V), was born at the castle. John died in 1399 and his exiled son, Henry Bolingbroke, returned to overthrow Richard II and seize the Crown. Following his coronation as Henry IV, Monmouth became a Royal castle once more.


Monmouth Castle remained relatively unscathed by the rebellion of Owain Glynd┼Ár although, following an attack on Grosmont Castle in 1405, a skirmish was fought within the town's outskirts. The castle continued to be maintained after the rebellion and in 1440 Henry VI built a twin towered gatehouse although this does not seem to have been fully completed. However, by the sixteenth century the castle was in disrepair although the Great Hall and some portions of the original Keep were maintained to serve as the assize courts.


During the Civil War the strategic importance of Monmouth meant the castle was reactivated and garrisoned for the Royalists. They held it until September 1644 when it was captured by Parliamentary forces by a ruse. It was retaken for the Royalists by Lord Charles Somerset in November 1644. The castle then remained in their hands until October 1645 when it was besieged by a Parliamentary army under Colonel Edward Massey, Governor of Gloucester. Monmouth Castle was badly damaged during the siege due to attempts by the Parliamentarians to undermine the structure and in 1647 the Great Round Keep was demolished to prevent any further military use.


In 1673 the Henry Somerset, Marquis of Worcester and Lord Lieutenant of Monmouthshire cleared the ruins of the Great Round Keep and used the stone to build Great Castle House on the same site. This residence was intended to replace his former palatial seat at Raglan Castle that had also suffered during the Civil War. The new structure later served in a variety of functions including a lodging for the assize Judges and, after the courts moved out of the Great Hall in 1724, it was then used a girls' school. In 1875 the castle became the headquarters of the Royal Monmouthshire Militia and the house was used as both the Officers' Mess and as administrative buildings. The Regiment became part of the Royal Engineers in 1877. The site remains in military occupation today but also incorporates a museum.





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What's There?

Monmouth Castle has undoubtedly seen better days. Little remains of the medieval castle other than the ruins of a twelfth century Keep and thirteenth century hall. Great Castle House survives and today hosts the small military museum. In the town, Monnow Bridge, a unique surviving example of a British medieval bridge, is worth the trip alone! Portions of the town's East Gate also survive embedded in a modern building.

Monmouth Castle and Walled Town. The town was located between the Rivers Monnow and Wye. The castle was at the western extremity of the town.

Great Tower. This was built circa-1150 and later extensively modified. It was similar in style to the contemporary structure at Chepstow Castle.

Hall Block. The hall was added by Edmund Crouchback, Earl of Lancaster in the mid-thirteenth century.

Great Castle House. This structure was built in 1673 by Henry Somerset, Marquis of Worcester over the ruins of the Great Round Keep that had been partially demolished following the Civil War. Stone from that structure was re-used to build the house.

High Ground. The castle was built upon the high ground overlooking the River Monnow.

Monnow Bridge. The Monnow Bridge is the only surviving example of a medieval fortified bridge in mainland Britain. The remarkable structure was built around 1300 and is similar to structures that would have existed at many other towns including Hereford and Worcester.

Getting There

Monmouth Castle is easily found in the town centre. There is no car parking (for visitors) at the castle itself but ample facilities nearby with one option shown below.

Car Parking Option

NP25 3EQ

51.808907N 2.718712W

Monmouth Castle

NP25 3BS

51.812502N 2.715838W

Monnow Fortified Bridge

Monnow Street, NP25 3EG

51.809030N 2.720025W

East Gate Remains

Dixton Road, NP25 3DJ

51.813259N 2.710472W