When two cardinals came to England at the end of 1337 to make peace between Edward III and Philip VI, the Duke of Cornwall is said to have met the cardinals outside the City of London, and in company with many nobles to have conducted them to the King Edward. On 11 July 1338 his father, who was on the point of leaving England for Flanders, appointed him guardian of the kingdom during his absence, and he was appointed to the same office on 27 May 1340 and 6 October 1342; he was of course too young to take any save a nominal part in the administration, which was carried on by the council. In order to attach John, Duke of Brabant, to his cause, the king in 1339 proposed a marriage between the young Duke of Cornwall and John's daughter Margaret, and in the spring of 1345 wrote urgently to Pope Clement VI for a dispensation for this marriage.