 In spite of his participation in the baronial reform movement , Gloucester still maintained the trust of the king . He , Gaveston and the Earl of Warenne were the only earls to accompany the king on a Scottish campaign in 1310 – 11 . In March 1311 , while the Ordinances were still in the workings , Gloucester was appointed guardian of the realm while the king was still in Scotland . There are signs that he might have fallen out with Thomas , Earl of Lancaster – who was at this point the leader of the opposition against the king – over a feud between two of their respective retainers . When Gaveston once more returned from exile , however , Gloucester sided with the baronial opposition . The earls divided the country into different parts for defence , and Gloucester was given charge of the south . In June 1312 , Gaveston was captured by Guy de Beauchamp , Earl of Warwick , who was working in cooperation with Lancaster . Aymer de Valence , Earl of Pembroke , who had the custody of Gaveston and had guaranteed his safety to the king , appealed to Gloucester , as Gaveston 's kinsman , for assistance . Gloucester , however , refused to help , and Gaveston was killed . This act brought the country to the brink of civil war , and Gloucester was one of the few men who was still trusted enough by both sides to be able to take on a role as mediator . In the following months , he was among the main negotiators working towards an agreement between the king and the offending earls , an effort that was at least temporarily successful . 
