A plot to carry off the young Mortimers was defeated; but Mowbray, the earl marshal, who had been privy to it, raised a rebellion in the north supported by Archbishop Scrope of York.
The manor, then called Bellus Locus or Beaulieu on account of its beautiful situation, was afterwards granted to the Mortimers, in whose family it continued until it was merged in the crown on the accession of Edward IV.
In the 14th century the castle was held by the Mortimers, from whom it passed to the Yorkists.
He was released, but in 1282 he revolted again, and was killed in a skirmish with the Mortimers, near Builth in central Wales.
Edward I.), given to the Mortimers and to Leicester (under Edward III.
In 1402 he routed the forces of the Mortimers at Bryn Glas near Knighton in Maesyfed, where he captured Sir Edmund Mortimer, the uncle and guardian of the legitimate heir to the English throne, the young earl of March.
The Yorkist faction seems to have been strongest in the eastern portion of the Principality, where the Mortimers were all-powerful, but later the close connexion of the house of Lancaster with Owen Tudor, a gentleman of Anglesea (beheaded in 1461) who had married Catherine of France, widow of Henry V., did much to invite Welsh sympathy on behalf of the claims of Henry Tudor his grandson, who claimed the English throne by right of his grandmother.
The earldom of Ulster, the old inheritance of the De Burghs, had descended to him from Lionel, duke of Clarence; the earldom of March came from the Mortimers, and the dukedom of York and the earldom of Cambridge from his paternal ancestry.