St Quentin's Castle, which is also known as Llanblethian Castle, was built in the early twelfth century in the form of a ringwork fortification. It was substantially rebuilt around 1312 by Gilbert de Clare, Earl of Gloucester into a courtyard castle. Dominating the new structure was a huge new gatehouse that was later used as a prison.



Southern Wales was conquered by Robert Fitzhamon, Baron of Gloucester in the late eleventh century. By the time of his death in 1106, he had advanced as far west as the River Ogmore which put the entire Vale of Glamorgan under his control. This included a parcel of lands known as Llanblethian which he granted to one of his followers, Herbert de St Quentin, around 1102. It was probably Herbert who raised the first fortification on the site.


The castle was built on a spur of high ground overlooking a bend in the River Thaw. This provided strong natural defences on the north, west and south sides due to the steep scarps down to the river. It was initially raised as an earth and timber ring-and-bailey fortification. Later in the twelfth century, a rectangular stone Keep was built within the ring.


The castle remained with the St Quentin family until 1233 at which time it was seized by Richard Siward. He was a mercenary but had fallen out of Royal favour and had seen his lands confiscated. His patron - Richard Marshal, Earl of Pembroke - had supported him and probably helped him acquire Llanblethian  (including St Quentin Castle) as compensation for loss of his English estates. Siward was later pardoned by the King and allowed to keep his Glamorgan acquisitions. However, he was declared an outlaw in 1245 and his property passed to Richard de Clare, Earl of Gloucester. It was his grandson, Gilbert de Clare, who commenced rebuilding of the castle around 1307.


Gilbert de Clare significantly enlarged the footprint of the castle fully enclosing the twelfth century Keep within the new courtyard. A large twin-towered gatehouse, which has similarities with the de Clare's Caerphilly Castle, was built on the vulnerable eastern side whilst a stone curtain wall enclosed a broadly rectangular courtyard. A substantial rectangular tower was built on the north-east side and perhaps incorporated the high status accommodation. Another substantial tower, this time in a polygonal configuration, occupied the south-east corner. There was a minor tower on the north-west side and perhaps another on the south-west.


Gilbert de Clare was killed at the Battle of Bannockburn (1314) and work on the castle seemingly came to an end at this time. In 1317 the castle was granted to Hugh Despenser and retained by the family even after his downfall. Edward Despenser was born there in 1375 but thereafter evidence of high-status occupation becomes scant. By the fifteenth century the gatehouse was being used as a local prison. It was reported as ruinous by 1741 but the ground floor chambers were later converted into a dwelling house which was still occupied in 1820 but abandoned shortly after.





Cadw (2017). St Quintin's Castle, GM094. Cardiff.

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What's There?

St Quentin's Castle (also known as Llanblethian Castle) is in the care of CADW but is an unstaffed property. The most substantial remains are of the gatehouse but the ruins of the twelfth century Keep are also visible.

St Quentin's Castle Layout. Originally a ring-and-bailey fortification, Gilbert de Clare rebuilt St Quentin's Castle into a courtyard fortification during the early fourteenth century. The original Keep was completely enclosed within the courtyard and a large twin-towered gatehouse was built to protect the vulnerable eastern side.

Gatehouse. The twin-towered gatehouse was constructed from grey lias stone with ashlar dressings. It bears many similarities with the de Clare's fortification at Caerphilly Castle.

Castle Entrance. The impressive entrance passage was used as a dwelling house in the early nineteenth century.

Gatehouse Interior. The first floor of the gatehouse was a single room (although there may have been wooden partitions).

Keep. The only visible remains of the original castle raised by the St Quentin family and those of the Keep. This was originally a rectangular tower set within the ringwork defences of the original fortification.

Getting There

St Quentin's Castle is found off Castle Street in Llanblethian. There is a dedicated car park for visitors.

St Quentin's Castle

CF71 7FA

51.457514N 3.455938W