In the years to come, Montagu acted as Edward's closest companion. In April 1331, the two went on a secret expedition to France, disguised as merchants so they would not be recognised. In September of the same year, Montagu held a tournament at Cheapside, where he and the king were costumed as Tartars. From 1333 onwards, Montagu was deeply engaged in the Scottish Wars, and distinguished himself at the Siege of Berwick and the Battle of Halidon Hill. It was after this event that his lordship over the Isle of Man was recognised, a right he held from his grandfather. The lordship was at the moment of a purely theoretical nature, however, since the island was still under Scottish control.