On the death of his father, Edward the Elder, in 924, Athelstan was elected king of Wessex and Mercia, where he had been brought up by his aunt, Aethelflaed, Lady of the Mercians. Crowned king of the whole country at Kingston on Sept. 4, 925, he proceeded to establish boundaries and rule firmly. He annexed the Viking kingdom of York in 927. His dominion was significantly challenged in 937 when Constantine of the Scots, Owain of Strathclyde, and Olaf Guthfrithson, claimant of the kingdom of York, joined forces and invaded England. They were routed at Brunanburh.

Six of Athelstan's extant codes of law reveal stern efforts to suppress theft and punish corruption. They are notable in containing provisions intended to comfort the destitute and mitigate the punishment of young offenders. The form and language of his many documents suggest the presence of a corps of skilled clerks staffed by the cathedral of Winchester. Both his charters and the silver coinage he issued through strictly controlled regional mints bore the proud title Rex totius Britanniae (“King of all Britain”).