The Midland kingdom of Mercia dominated southern England, but their supremacy came to an end in 825 when they were decisively defeated by Ecgberht at the Battle of Ellendun.

[2] In the same year Ecgberht sent his son Æthelwulf to conquer the Mercian sub-kingdom of Kent (the area of the modern county plus Essex, Surrey and Sussex) and appointed him sub-king.

Æthelwulf and Ecgberht may not have intended a permanent union between Wessex and Kent as they both appointed sons as sub-kings and charters in Wessex were attested (witnessed) by West Saxon magnates, while Kentish charters were witnessed by the Kentish elite; both kings kept overall control and the sub-kings were not allowed to issue their own coinage.

[5] Viking raids increased in the early 840s on both sides of the English Channel, and in 843 Æthelwulf was defeated by the companies of 35 Danish ships at Carhampton.

[6] In 851 Æthelwulf and his second son Æthelbald defeated the Vikings at the Battle of Aclea and, according to the Anglo-Saxon Chronicle, "there made the greatest slaughter of a heathen raiding-army that we have heard tell of up to this present day, and there took the victory".

[a] Æthelstan died in the early 850s, but the four younger brothers were successively kings of Wessex: Æthelbald from 855 to 860,[b] Æthelberht from 860 to 865, Æthelred I from 865 to 871 and Alfred the Great from 871 to 899.

[13] In 856, Æthelwulf returned to England with a new wife, Judith, daughter of Charles the Bald, king of the West Franks.

Æthelbald, with the support of Eahlstan, Bishop of Sherborne, and Eanwulf, Ealdorman of Somerset, refused to give up his kingship of Wessex.

[26] He appears to have been on good terms with his younger brothers and in a charter of 861 (S 330) he granted land to St Augustine's, Canterbury, in return for the abbot's continuing loyalty to him, Æthelred, and Alfred.

However, a charter of Æthelberht dated December 863 (S 333) is attested by Æthelred and Alfred as filius regis (king's son).

[28] Æthelberht granted immunity from royal and judicial services to Sherborne church in honour of the souls of his father Æthelwulf and his brother Æthelbald.

In 860, a Viking army sailed from the Somme to England and sacked Winchester, but they were then defeated by the men of Hampshire and Berkshire.

[31] In the late eighth and ninth centuries, the only denomination of coin produced in southern England was the silver penny.

[34] There was a considerable increase in the number of moneyers: twelve struck Inscribed Cross coins in Æthelwulf's reign and fifty in Æthelberht's.

This may have been due to a recoinage starting at the end of Æthelwulf's reign and continuing in Æthelberht's, when old coins were called in and melted down to make new ones.

There was also increasing standardisation of design in the coinage, reflecting greater royal control over currency and minting in the middle of the ninth century.