c.627-731. Early history of Lindsey
The kingdom of Lindsey (probably the same as the Parts of Lindsey in modern Lincolnshire) was known to Bede, and though it fell alternately under Northumbrian and Mercian control in the 7th century, a surviving regnal list shows that it did at one time boast its own kings. It was once thought that the last of these, Aldfrith, witnessed a single charter confirmed by Offa of Mercia (S 1183), but this is now thought to be more probably a mangled attestation of Offa's son Ecgfrith (see Kelly, Selsey, p. 54).
Most of the references to Lindsey in the 7th century come from Bede. In the earliest, Paulinus goes to Lindsey after converting Edwin and converts the nobleman (praefectus) Blæcca and his household in Lincoln (HE, ii.16). Bede goes on to report a story that mass baptisms took place in the river Trent near Littleborough in the presence of King Edwin, which suggests that Lindsey was already under Northumbrian influence at this point. Lindsey next emerges after the death of Oswald of Northumbria in 642, when the Lindsey monastery of Bardney was unwilling to receive the bones of St Oswald, "because he belonged to another kingdom and had once conquered them" (HE, iii.11); it took a miracle for them to change their minds, so, as one would expect in Bede's History, a miracle duly took place. In the time of Wulfhere of Mercia (658-75), Lindsey was part of the diocese of Mercia (HE, iv.3), but Wulfhere lost it to Northumbria when he fought Ecgfrith in around 670?675. In 678, Lindsey gained a bishop (HE, iv.12), and it was probably at the Battle of the Trent in the following year (see entry on 679) that Wulfhere's successor Æthelred regained Lindsey from Ecgfrith (HE, iv.12).
The return to Mercian control in 679 was the final change: from then on, Lindsey was under Mercian control, though it seems to have retained its kings at least until 731, when Bede mentions the kingdom of Lindsey as being part of Æthelbald of Mercia's Southumbrian dominions (HE, v.23).
D. Dumville, "The Anglian collection of royal genealogies and regnal lists", Anglo-Saxon England 5 (1976), pp.23-50 (for Lindsey, see p. 37)
B. Eagles, "Lindsey", in S. Bassett (ed.), The Origins of the Anglo-Saxon Kingdoms (London: 1989), pp.202-12
S. Kelly, Charters of Selsey (Oxford: 1998)
F. Stenton, "Lindsey and its Kings", Preparatory to Anglo-Saxon England (Oxford: 1970), pp.127-35