The first Gilbert de Clare is principally remembered as one of the barons of the Magna Carta; he died in 1230, leaving his son, Richard, as his heir. Richard, who was only 8 years old at the death of his father. On coming of age in 1243, he tightened his father's hold on the Welsh lords in the uplands and on the fringes of Glamorgan.
Earl Richard died in 1262 and was succeeded by his heir Gilbert ‘The Red’. The ever-present threat of attack on the castle at Cardiff, the administrative centre for the whole of the Glamorgan lordship, caused him to reconstruct its defences with a great sense of urgency. He constructed a central embattled wall to link the improved keep (remodelled for the better accommodation of the household) with the south gate and the Black Tower. On the east side of the embattled wall (the outer ward) were now provided permanent lodgings for the knights of Glamorgan and their grooms and men-at-arms, during their periods of garrison duty.
Gilbert died in 1295 and left a son of the same name. When his mother Joan died, Gilbert the younger was still under age but he inherited the lordship. What little we know of this new lord reflects well on his dealings with his neighbouring Welsh princes, but he fell in battle at Bannockburn in 1314 at the age of 23. The lordship passed to his sister Eleanor, who had married Hugh Despenser in 1306. Hugh Despenser was the first of the new family that retained the lordship for nearly a hundred years.