Æthelbald early revealed himself a hypocrite by marrying his stepmother, Judith. Swithun, the Bishop of Winchester, had some talks with Æthelbald, with the result that Æthelbald separated from Judith. She traded her dowry for money and returned to France, marrying Baldwin, the Count of Flanders. Their daughter, Matilda, would eventually marry William the Conqueror.

Æthelbaldís reign was peaceful, and he died an early but natural death five years afterwards. According to his fatherís will, Æthelred should now have been king, but since everyone, including Æthelred, agreed the will was unfair, Æthelbert instead ascended the throne.