"The chief political question in which Peckham was concerned was the Welsh war. The archbishop was anxious to put down the abuses in the Welsh church, and to bring it into greater harmony with English customs. ...he wrote to Llywelyn rebuking him for his infringements of the liberties of the church. In July 1280 he visited Wales, and made a friendly arrangement with Llywelyn... But a month later a letter of Peckham's, in which he asserted the reasonableness of Edward's claim to settle disputes on the marches by English customs, roused Llywelvn's wrath. The archbishop's ill-considered action led to the trouble which precipitated the end of Llywelyn's power. By the spring of 1282 the Welsh had broken out into open rebellion, and on 1 April Peckham ordered their excommunication. Towards the end of October Peckham joined the king at Rhuddlan, with the intention of endeavouring to mediate in person. On 31 Oct. he set out, against Edward's will, to meet Llywelyn... But prolonged discussion and negotiations between the archbishop and the Welsh prince failed to produce any terms to which Edward could give his consent."