Caerphilly Castle, covering 12 hectares, is one of the greatest surviving castles in the medieval Western world. It was the culmination of medieval defensive architecture with massive gates and waterworks, and is considered the first true example of a concentric castle in Britain. De Clare's design was so successful that it was used as a model for Edward I's castles in North Wales.
The mighty fortress of Gilbert de Clair was not the first on this site. Long before the Normans arrived, the Romans had built a fort some 1,200 years before de Clare embarked on a project that would create the largest non-royal castle in Britain. The scale of Caerphilly Castle is so enormous that the Tower of London could fit within its outer walls twice, and the Edwardian castles of Harlech, Beaumaris, Caernarfon, Conwy and Rhuddlan could be squeezed into it.
History of Caerphilly Castle
In 1268 De Clare began work on Caerphilly to protect his lands from the Welsh threat. Llewelyn did not sit idly by, he attacked the castle and destroyed de Clare's works. However, his attention was diverted by the invasion of Wales by Edward I after 1272, and de Clare continued to build the fortress. After Llewelyn's death, the Welsh military threat had diminished and Caerphilly's defensive capabilities were insignificant, so it became the administrative center of the vast De Clare lands.
De Clare died in 1295 and his son, also called Gilbert, completed his father's ambitious plans, so that Caerphilly Castle was virtually complete by the time of de Clare's second death at the Battle of Bannockburn in 1314. The castle passed to Gilbert's sister Eleanor, wife of Edward II's favorite, Hugh le Despenser. It remained in Despenser's hands until the 15th century, when it passed through marriage to Richard Beauchamp, Earl of Worcester, and eventually to the Herbert family of Pembroke.
Caerphilly Castle stands on a low island surrounded by a load-bearing wall. The design consists of an inner ward with round corner towers and a double-towered airlock providing access to the outer ward. The outer ward has an impressive gatehouse added in 1270. It may have been modeled on an earlier one at Tunbridge built by de Clare's father, Richard. The Caerphilly Castle building functioned as a separate entity that could be defended independently of the castle. This was an innovation for the time and predated similar features in Edwardian castles in north Wales.