Egbert then defeated all of Mercia in 829. The king of Northumbria submitted to him after the defeat of Mercia. He assumed the title (King of Mercia). This title was also on coins made in the former Mercian port of London. In 830 Wiglaf returned to power in Mercia, but the gains of Kent and southwest England remained with Wessex. Egbert died 4 February 839. He left a territory larger than any other Wessex king since Ine. He was the "bretwalda" or overlord of Anglo-Saxon England until Wiglaf returned in 830. Even so, he remained the most powerful king during his time.