 For most of the 8th century , Mercia was the dominant Anglo @-@ Saxon kingdom . Mercian influence in the south @-@ eastern kingdoms of Kent , East Anglia , and Essex continued into the early 820s under Coenwulf of Mercia . However , Coenwulf 's death in 821 marked the beginning of a period in which Mercia suffered from dynastic conflicts and military defeats that redrew the political map of England . Four ( possibly five ) kings , from what appear to be four different kin @-@ groups , ruled Mercia throughout the next six years . Little genealogical information about these kings has survived , but since Anglo @-@ Saxon names often included initial elements common to most or all members of a family , historians have suggested that kin @-@ groups in this period can be reconstructed on the basis of the similarity of their names . Three competing kin @-@ groups are recognizable in the charters and regnal lists of the time : the C , Wig and B groups . The C group , which included the brothers Coenwulf , Cuthred of Kent , and Ceolwulf I , was dominant in the period following the deaths of Offa of Mercia and his son Ecgfrith in 796 . Ceolwulf was deposed in 823 by Beornwulf , perhaps the first of the B group , who was killed fighting against the East Anglians in 826 . He was followed by Ludeca , not obviously linked to any of the three groups , who was killed in battle the following year . After Ludeca 's death , the first of the Wig family came to power : Wiglaf , who died in 839 or 840 . Beorhtwulf , who succeeded to the throne that year , is likely to have come from the B group , which may also have included the ill @-@ fated Beornred who " held [ power ] a little while and unhappily " after the murder of King Æthelbald in 757 . 
