Ecgberht was unable to maintain this dominant position, and within a year Wiglaf regained the throne of Mercia. However, Wessex did retain control of Kent, Sussex, and Surrey; these territories were given to Ecgberht's son Æthelwulf to rule as a subking under Ecgberht. When Ecgberht died in 839, Æthelwulf succeeded him; the southeastern kingdoms were finally absorbed into the kingdom of Wessex after the death of Æthelwulf's son Æthelbald in 860.