In 1460 at Calais, then belonging to the English crown, he was taken prisoner by the Earl of Warwick whilst on a military expedition during the Wars of the Roses. He there met the future Edward IV and was persuaded to defect to the Yorkist cause and fought for Edward at the Battles of Mortimer's Cross (1461), Barnet (1471) and Tewkesbury (1471). He was subsequently invested by Edward in 1471 as a Privy Counsellor (PC). He received commissions of Array. He was joint commander of the Army and held the office of Master of the King's Dogs in 1471. He was present when King Edward bestowed the title of Earl of Winchester upon Louis Seigneur de la Gruthuyse in 1472.