 He was appointed guardian of Scotland in 1306, but with the accession of Edward II to the throne and the consequent rise of Piers Gaveston to power, his influence declined.He became prominent among the discontented nobles, but in 1312, after the Earl of Warwick betrayed him by executing the captured Gaveston, he left the allied lords and joined the King.Valence was present at Bannockburn in 1314, and later helped King Edward defeat Thomas of Lancaster.