Caerphilly Castle is one of the great medieval castles of western
Europe. Several factors give it this pre-eminence - its immense size
(1.2h), making it the largest in Britain after Windsor, its large-scale
use of water for defence and the fact that it is the first truly
concentric castle in Britain. Of the time of its building in the late
13th century, it was a revolutionary masterpiece of military planning
One of Henry III's most powerful and ambitious barons, Gilbert de
Clare, lord of Glamorgan, built this castle. His purpose was to secure
the area and prevent lowland south Wales from falling into the hands of
the Welsh leader Llywelyn the Last, who controlled most of mid and north
Wales. De Clare built other castles on the northern fringes of his
territory for the same purpose, such as Castell Coch. He had seized the
upland district of Senghenydd, in which Caerphilly lies, from the Welsh
in 1266 to act as a buffer against Llywelyn's southward ambitions.
Llywelyn realised the threat and tried but failed to prevent the castle
from being built; it was begun on 11 April 1268, was attacked by
Llywelyn in 1270, and was begun again in 1271. This time it was
completed without hindrance. Its message was not lost on Llywelyn, who
retreated northwards. Apart from the remodelling of the great hall and
other domestic works in 1322-6 for Hugh le Despenser, no more
alterations were carried out, making it a very pure example of late
13th-century military architecture.
