Æthelwulf was first recorded in 825, when Egbert won the crucial Battle of Ellandun in Wiltshire against King Beornwulf of Mercia, ending the long Mercian ascendancy over southern England. Egbert followed it up by sending Æthelwulf with Eahlstan, Bishop of Sherborne, and Wulfheard, Ealdorman of Hampshire, with a large army into Kent to expel sub-king Baldred. Æthelwulf was descended from kings of Kent, and he was sub-king of Kent, and of Surrey, Sussex and Essex, which were then included in the sub-kingdom, until he inherited the throne of Wessex in 839. His sub-kingship is recorded in charters, in some of which King Egbert acted with his son's permission, such as a grant in 838 to Bishop Beornmod of Rochester, and Æthelwulf himself issued a charter as King of Kent in the same year. Unlike their Mercian predecessors, who alienated the Kentish people by ruling from a distance, Æthelwulf and his father successfully cultivated local support by governing through Kentish ealdormen and promoting their interests. In Abels' view, Egbert and Æthelwulf rewarded their friends and purged Mercian supporters. Historians take differing views on the attitude of the new regime to the Kentish church. At Canterbury in 828 Egbert granted privileges to the bishopric of Rochester, and according to the historian of Anglo-Saxon England Simon Keynes, Egbert and Æthelwulf took steps to secure the support of Archbishop Wulfred. However, the medievalist Nicholas Brooks argues that Wulfred's Mercian origin and connections proved a liability. Æthelwulf seized an estate in East Malling from the Canterbury church on the ground that it had only been granted by Baldred when he was in flight from the West Saxon forces; the issue of archiepiscopal coinage was suspended for several years; and the only estate Wulfred was granted after 825 he received from King Wiglaf of Mercia.