Edwy, to judge from the disproportionately large numbers of charters issued during his reign, seems to have been weakly lavish in the granting of privileges, and soon the chief men of Mercia and Northumbria were disgusted by his partiality for Wessex.
LEthelbald of Mercia seems to have taken advantage of this campaign to ravage Northumbria.
In the 7th century the supremacy over Lindsey alternated between Mercia and Northumbria, but few historical references to the district are extant until the time of Alfred, whose marriage with Ealswitha was celebrated at Gainsborough three years before his accession.
In 779 Offa of Mercia defeated him and took Bensington.
It is probable that down to the end of the 7th century, if not still later, the court poets of Northumbria and Mercia continued to celebrate the deeds of Beowulf and of many another hero of ancient days.
After Oswio's victory over Penda in 654-655 he annexed the northern part of Mercia to his kingdom and acquired a supremacy over the rest of England similar to that held by his predecessors.
It is probable that no actual conflict took place, and in 959, on Edwy's death, Edgar acceded peaceably to the combined kingdoms of Wessex, Mercia and Northumbria.
In 673 Archbishop Theodore divided the East Anglian diocese into two, Elmham being the seat of the northern, Dunwich that of the southern bishop. A long blank follows in the history of this kingdom, until in 792 we find Offa of Mercia slaying iEthelberht, king of East Anglia, who is said to have been his son-in-law.
They encamped in Nottingham in 868, and Northern Mercia was soon in their hands; in 870 Edmund, king of the East Anglians, fell before them.
There are Saxon still extant an impression of the seal of Offa of Mercia royal (A.D.