939. Olaf Guthfrithsson becomes king in York
939/40. Olaf expands southwards, takes Five Boroughs, to Watling Street

Olaf Guthfrithsson, who was defeated by Æthelstan at Brunanburh in 937, returned from Dublin to England in the two months between Æthelstan's death and the end of 939 (see Beaven, p.2, drawing on Irish chronicles), and had probably occupied York by the end of 939. The Anglo-Saxon Chronicle notes that the Northumbrians were false to their pledges and chose Olaf from Ireland as their king, which suggests there was no resistance.

The Chronicle notes that Olaf next took Tamworth by storm, and carried away much plunder from there. Then King Edmund besieged King Olaf and Archbishop Wulfstan at Leicester, and could have taken them if they had not escaped by night. Simeon of Durham, writing in the 12th century, adds some details, noting that Olaf marched south from York to Northampton, and when that siege failed he went on to Tamworth, and ravaged the area. On his return to Leicester and meeting with Edmund, serious fighting was averted by the two archbishops, Oda and Wulfstan, who reconciled the kings and helped conclude a truce. By the terms of the truce, Watling Street became the boundary between Edmund's kingdom and Olaf's.

Since Oda was not transferred from Ramsbury to Canterbury until 941 (see S 475 and 476), it may be that his presence at Leicester as archbishop in 940 is a literary embellishment of Simeon's to balance the other archbishop. But that the boundary was returned to Watling street is shown independently from Edmund's reconquests of 942 and 944.

The return of the border to Watling Street meant that in a single year Olaf Guthfrithsson had reversed the reconquest of the Danelaw which Edward and Æthelflæd had managed in the 910s, and Æthelstan had apparently sealed in the 920s and 930s. It is also worth noting that Wulfstan, archbishop of York, was acting on behalf of the Norse king: his taking of sides here makes it easier to understand why King Eadred would order Wulfstan's arrest in 952 when another Norse king was in charge of York (q.v.).

M. Beaven, "King Edmund I and the Danes of York", English Historical Review 139 (1918), pp.1-9