In 1263, Gilbert de Clare, also known as "Red Gilbert" because of the colour of his hair, inherited the family lands. Opposing him in Glamorgan was the native Welsh prince Llywelyn ap Gruffudd. Llywelyn had taken advantage of the chaos of the civil war in England between Henry III and rebel barons during the 1260s to expand his power across the region. In 1265 Llywelyn allied himself with the baronial faction in England in exchange for being granted authority over the local Welsh magnates across all the territories in the region, including Glamorgan. De Clare believed his lands and power were under threat and allied himself with Henry III against the rebel barons and Llywelyn.