William Marshal, 1st Earl of Pembroke
King John was a man who was disliked by many of his barons and Earls.  He knew this and distrusted them.  When Marshal went over to protect his lands in Ireland the King made him give one of his sons as hostage to make sure that Marshal was not disloyal to him.  King John sometimes took lands away from Marshal and at other times gave them back.  There was strife all during the reign of King John but Marshal remained loyal to the King throughout.