Gilbert's son, also called Gilbert de Clare, inherited the castle, but he died fighting at the battle of Bannockburn in 1314 while still quite young. The family's lands were initially placed under the control of the Crown, but before any decision could be taken on the inheritance, a revolt broke out in Glamorgan. Anger over the actions of the royal administrators caused Llywelyn Bren to rise up in January 1316, attacking Caerphilly Castle with a large force of men. The castle withstood the attack, but the town was destroyed and the rebellion spread. A royal army was despatched to deal with the situation, defeating Bren in a battle at Caerphilly Mountain and breaking the Welsh siege of the castle.