937. Battle of Brunanburh
The battle of Brunanburh is commemorated in the Anglo-Saxon Chronicle by an Old English poem. From that poem we learn that Æthelstan and his brother Edmund won a victory at Brunanburh (unidentified), against Constantine of Scotland and Olaf, that they slew five young kings and seven of Olaf's earls, and a numberless host of seamen and Scots. The prince of the Norsemen was driven back to Dublin, and Constantine also returned to his own land.
The Olaf who was defeated at Brunanburh was not the Olaf Cuaran (son of Sihtric) whom Guthfrith came to York to support in 927, but Guthfrith's own son, somewhat confusingly also called Olaf. This Olaf Guthfrithsson became king of Dublin in 934, when his father died, and so appropriately is driven back to Dublin at battle's end (see Stenton, pp.342-3).
F. Stenton, Anglo-Saxon England, 3rd edn (Oxford: 1971)