The subsequent 747 council of Clovesho and a charter Æthelbald issued at Gumley in 749—which freed the church from some of its obligations—may have been responses to Boniface's letter.

He was succeeded briefly by Beornred, of whom little is known, but within a year, Offa, the grandson of Æthelbald's cousin Eanwulf, had seized the throne, possibly after a brief civil war.

[4] Guthlac was a Mercian nobleman who abandoned a career of violence to become first a monk at Repton Abbey, and later a hermit living in a barrow at Crowland, in the East Anglian fens.

[3] Other than his father, Alweo, little of Æthelbald's immediate family is known, although in the witness list of two charters[10] a leading ealdorman named Heardberht is recorded as his brother.

At the start of Æthelbald's reign, both Kent and Wessex were ruled by strong kings; Wihtred and Ine, respectively.

The Anglo-Saxon Chronicle also tells how when Cuthred succeeded Aethelheard to the throne of Wessex, in 740, he "boldly made war against Aethelbald, king of Mercia".

This could have been an obligation placed on Cuthred by Mercia; earlier kings had similarly assisted Penda and Wulfhere, two strong seventh-century Mercian rulers.

Æthelbald, who might have been allied with Óengus,[21] the king of the Picts, took advantage of Eadberht's absence from Northumbria to ravage his lands, and perhaps burn York.

It is possible that the chronicler was merely adding Egbert's name to Bede's original list of seven, rather than claiming that no other kings achieved similar powers in England.

[30] Further evidence of Æthelbald's power, or at least his titles, is provided by an important charter of 736, the Ismere Diploma, which survives in a contemporary (and possibly original) copy.

[33] In 745–746, the leading Anglo-Saxon missionary in Germany, Boniface, along with seven other bishops, sent Æthelbald a scorching letter reproaching him for many sins—stealing ecclesiastical revenue, violating church privileges, imposing forced labour on the clergy, and fornicating with nuns.

[32] The letter implored Æthelbald to take a wife and abandon the sin of lust: We therefore, beloved son, beseech Your Grace by Christ the son of God and by His coming and by His kingdom, that if it is true that you are continuing in this vice you will amend your life by penitence, purify yourself, and bear in mind how vile a thing it is through lust to change the image of God created in you into the image and likeness of a vicious demon.

Remember that you were made king and ruler over many not by your own merits but by the abounding grace of God, and now you are making yourself by your own lust the slave of an evil spirit.

[34]Boniface first sent the letter to Ecgberht, the archbishop of York, asking him to correct any inaccuracies and reinforce whatever was right; and he requested Herefrith, a priest whom Æthelbald had listened to in the past, to read and explain it to the king in person.

[32] A claim made in a ninth-century list of donations from the abbey of Gloucester that Æthelbald had "stabbed—or smitten" to death the kinsman of a Mercian abbess has also contributed negatively to his reputation.

Two years after this, in 749, at the synod of Gumley, Æthelbald issued a charter that freed ecclesiastical lands from all obligations except the requirement to build forts and bridges—obligations which lay upon everyone, as part of the trinoda necessitas.

Æthelbald was buried at St Wystan's Church, Repton, in a crypt which still can be seen; a contemporary is reported to have seen a vision of him in hell, reinforcing the impression of a king not universally well-regarded.

[42] The monastery church on the site at that time was probably constructed by Æthelbald to house the royal mausoleum; other burials there include that of Wigstan.

[32][43][44] A fragment of a cross shaft from Repton includes on one face a carved image of a mounted man which, it has been suggested, may be a memorial to Æthelbald.

[45][46] According to a story recorded by the 16th-century antiquarian John Leland, and derived by him from a now lost book in the possession of the Earls of Rutland at Belvoir Castle, there was once a King Alfred III of Mercia, who reigned in the 730s.