Offa was the son of Thingfrith (m) and Eowa (f) and became king in 757 A.D after the assassination of Aethelbald who, according to Bede’s Historia Ecclesiastica was murdered in the middle of the night by his own guards.
Offa eventually consolidated his position by marrying his daughters to other English kings, his daughter Eadburh was married to the king of Wessex, and his daughter Aelfflaed was married to the king or Northumbria. This in part resulted in him being the first ruler to be called “King of the English” although not in the sense we understand it today as there were other kings or ‘kingletts’ in England, but Offa was master of everything south of the Humber. He became overlord of East Anglia when he had Aethelberht II beheaded.
Offa is seen as the first king to unite the various tribes of England, he did this not out of some altruistic ambition to create a ‘whole’ country, but out of personal ambition. He was ruthless in putting down a rebellion in the south, and he had Offa’s Dyke built, the dyke runs for 149 miles along the boarders of the kingdoms of Mercia and Wales.
He is known to have communicated with Charlemagne on several matters, the most notable was the suggestion that Charlemagne’s son Charles should marry Offa’s daughter Aelfflaed (before she was sent north) but when Offa suggested that his son Ecgfrith should also marry Charlemagnes daughter Bertha he was outraged and broke all contact with Britain and forbade all English ships permission to land at any of his ports which in effect meant anywhere in modern western Europe. This situation continued for about a year until communications were re-established. It is known that Charlemagne wrote to Offa seeking support for his position regarding the two Spanish bishops Felix and Elipandus, accused of heresy; this letter is still in existence and is the first surviving document in English diplomatic history.
Offa also travelled to Rome in order to strengthen ties with the papacy. Offa had come into conflict with the church, mainly with Jaenberht the Archbishop of Canterbury, possibly over his opposition to Offa’s wish to have his son Ecgfrith crowned while he was still alive in order to ensure the succession. Ecgfrith is the first recorded coronation, (unfortunately it was also a waste of time he only outlived his father by a matter of months and died childless.) As a result Offa persuaded the pope Adrian I to split the Diocese of Canterbury and therefore created the diocese of Litchfield.
Other things worth noting regarding Offa are the comments from the papal delegate Alcuin praised Offa for his piety and for his views on education, it is believed that not only was he literate but his wife Cynethryth and their children were too. Cynethryth is also the only Anglo-Saxon queen to be depicted on a coin.
Offa died in 796 A.D after ruling for more than thirty years. He was buried in Bedford. The Mercian rule came to an end just nine years later when they were defeated at the battle of Ellendun (near Swindon in Wiltshire) in 825 A.D and the crown passed to Wessex.