ventually, in 1317, the inheritance was Partitioned between Earl Gilbert's three younger sisters. In the meantime, however the estates were in the king's hands, and in Glamorgan the royal custodians tactlessly provoked the Welsh into a brief but furious rebellion during the early weeks of 1316. At the root of the trouble was the continued disenchantment of the native community in the upland commotes. The royal administrators failed to understand the delicate nature of the relationship on which a smooth running of the lordship depended.

The revolt was led by an influential Welsh nobleman, Llywelyn Bren, the son of Gruffudd ap Rhys of Senghennydd, whom Gilbert de Clare had dispossessed in 1267. Llywelyn spoke for both native lords and people, and for their disillusion with the efforts of the first royal custodian in Glamorgan, Bartholomew de Badlesmere. The situation worsened with the appointment of Payn de Turberville in July 1315.


The rebellion broke on 28 January 1316 and was signalled with Llywelyn's attack on Caerphilly Castle with an alleged force of some 10,000 men. The keeper of the castle, William de Berkerolles, was captured and a number of other people attending a court outside the stronghold walls were either killed or abducted. The town and its mills were destroyed, though the castle itself was not taken. The only recorded damage was to a gate and drawbridge, so badly burnt it required replacement. Meanwhile the revolt spread through Glamorgan, with devastating and disastrous consequences.


A large royal army was mustered to quell the insurgents. Confronted by such a force Llywelyn and his men retreated to upland Senghennydd. The English plan involved converging on the defenders from two directions, with one wing moving south from the lordship of Brecon and another setting out from Cardiff on 12 March. Caerphilly Mountain was strongly defended by the Welsh, and the royal force had to outflank the ridge and then fight its way along it. Caerphilly Castle was relieved and garrisoned anew. Llywelyn Bren surrendered to the king's mercy on 18 March, and was imprisoned with his family in the Tower of London.