Little is known of Anna's life or his reign, as few records have survived from this period. In 631 he may have been at Exning, close to the Devil's Dyke. In 645 Cenwalh of Wessex was driven from his kingdom by Penda and, due to Anna's influence, he was converted to Christianity while living as an exile at the East Anglian court. Upon his return from exile, Cenwalh re-established Christianity in his own kingdom and the people of Wessex then remained firmly Christian.
Around 651 the land around Ely was absorbed into East Anglia, following the marriage of Anna's daughter Æthelthryth. Anna richly endowed the coastal monastery at Cnobheresburg. In 651, in the aftermath of an attack by Penda on Cnobheresburg, Anna was forced to flee into exile, perhaps to the western kingdom of the Magonsæte. He returned to East Anglia in about 653, but soon afterwards the kingdom was attacked again by Penda and at the Battle of Bulcamp the East Anglian army, led by Anna, was defeated by the Mercians, and both Anna and his son Jurmin were killed. Anna was succeeded by his brother, Æthelhere. Botolph's monastery at Iken may have been built in commemoration of the king. After Anna's reign, East Anglia seems to have been eclipsed by its more powerful neighbour, Mercia.
The kingdom of East Anglia (Old English: Ēast Engla Rīce) was a small independent Anglo-Saxon kingdom that comprised what are now the English counties of Norfolk and Suffolk and perhaps the eastern part of the Cambridgeshire Fens.
In contrast to the kingdoms of Northumbria, Mercia and Wessex, little reliable evidence about the kingdom of the East Angles has survived, because of the destruction of its monasteries and the disappearance of the two East Anglian sees that occurred as the result of Viking raids and settlement. The main primary sources for information about Anna's life and reign are the Historia ecclesiastica gentis Anglorum (Ecclesiastical History of the English People), completed in Northumbria by Bede in 731, and the Anglo-Saxon Chronicle, initially written in the ninth century, which mentions Anna's death. The mediaeval work known as the Liber Eliensis, written in Ely in the twelfth century, is a source of information about Anna's daughters Æthelthryth and Seaxburh, and also describes Anna's death and burial.
Anna was the son of Eni, a member of the ruling Wuffingas family, and nephew of Rædwald, king of the East Angles from 600 to 625. East Anglia was an early and long-lived Anglo-Saxon kingdom in which a duality of a northern and a southern part existed, corresponding with the modern English counties of Norfolk and Suffolk.