716. Ceolred of Mercia dies
Æthelbald, grandson of Eowa, succeeds to Mercia
The Anglo-Saxon Chronicle reports that Æthelbald was the son of Alweo, the son of Eowa, the son of Pybba (ASC 716), so his ancestry goes back not to Penda but to his brother Eowa. During the reign of Ceolred, who was descended from Penda, Æthelbald was in exile. Felix's near-contemporary Life of St Guthlac reports Æthelbald's several visits to the hermit Guthlac, once in the company of Wilfrid (chapter 40), and on one occasion Guthlac comforted Æthelbald, assuring him that Ceolred would soon die and Æthelbald would assume his rightful place as lord of the Mercians (chapter 49).
Bede remarks famously that by 731, all the southern kingdoms up to the Humber were subject to Æthelbald of Mercia (HE, v.23; Bede names specifically Kent, the kingdom of Essex, the East Angles, the West Saxons, the kingdom of the Mercians and those west of the Severn (the Magonsætan), the kingdom of the Hwicce and the kingdom of Lindsey). Corroboration of some of this appears in the entries for c.670-c.790 (for the rulers of the Hwicce signing as Æthelbald's subkings), 725-760s (for Mercians being appointed as archbishop of Canterbury in Kent), 726 (for Æthelheard of Wessex appearing in Æthelbald's entourage). Several charters granting freedom from tolls show that Æthelbald had important commercial interests in London (see Kelly for discussion). The same impression of wide powers is given by the famous Ismere charter of 736 (S 89), where Æthelbald is called in the text "ruler not only of the Mercians but of all the provinces that go by the general name of 'South English'", and "ruler of Britain" in the witness-list.
Æthelbald occupied West Saxon Somerton in 733, and devastated Northumbria (perhaps burning York) while Eadberht of Northumbria was off fighting the Picts in 740. In 743 Æthelbald and Cuthred of Wessex both fought the Britons, with Cuthred perhaps acting under Æthelbald's orders. However, Cuthred was not quiet under the Mercian yoke, and fought Æthelbald in 750 and managed to put him to flight in 752. The West Saxons may have been back under some sort of control in 757, given that a charter of Æthelbald's from that year gives him the style "king not only of the Mercians but also of surrounding peoples" and includes the attestation of Cynewulf of Wessex (S 96). Æthelbald was killed in 757.
In about 747, Boniface and seven other missionary bishops wrote a letter to Æthelbald (EHD 177), praising his good works and alms-giving and keeping the peace, and blaming him for not taking a wife but instead fornicating with nuns, and also for violating the privileges of churches and stealing their revenues. In response, Æthelbald issued a charter in 749 which stated clearly and at length that the churches should be free of all forms of public taxation, and churchmen free of all works and burdens, save those which are exacted from everyone (S 92; see Keynes for discussion).
S. Kelly, "Trading privileges from eighth-century England", Early Medieval Europe 1(1) (1992), pp.3-28
S. Keynes, "The reconstruction of a burnt Cottonian manuscript: The case of Cotton MS. Otho A. I", British Library Journal 22.2, pp.113-60