[1] William of Malmesbury declared that, after Cœnwulf: "the kingdom of the Mercians declining, and if I may use the expression, nearly lifeless, produced nothing worthy of historical commemoration."

Indicating the year 822, the Annales Cambriae states: "The fortress of Degannwy (in Gwynedd) is destroyed by the Saxons and they took the kingdom of Powys into their own control."

A later charter depicts a disturbed state of affairs during Ceolwulf's reign: "After the death of Cœnwulf, king of the Mercians, many disagreements and innumerable disputes arose among leading persons of every kind—kings, bishops, and ministers of the churches of God—concerning all manner of secular affairs".

In 823, sometime after 26 May, on which date he granted land to Archbishop Wulfred in exchange for a gold and silver vessel, Ceolwulf was overthrown.

According to a tradition preserved at Evesham, Ceolwulf's daughter Ælfflæd married Wigmund, the son of Wiglaf, King of Mercia (827–839).