The Historia Brittonum offers no dates of its own for Urien's life, and scholars cannot date the death of Theodric with certainty. The reckoning of reigns of Bernician rulers from the text implies his rule ended at 579, but his successor, Hussa of Bernicia, does not appear in Northumbrian sources, implying that he may have been a pretender. The next king all sources agree on is Æthelfrith, who took the throne c. 593, and so Urien could have died as late as this. See Jackson, Kenneth H., Language and History in Early Britain (Edinburgh: University Press 1953) pp. 707–708, Lovecy, Ian, 'The end of Celtic Britain: a sixth-century battle near Lindisfarne', Archaeologia Aeliana, Series 5, vol. 4, pp. 31–45 doi:10.5284/1060643, and David Dumville, in a lecture to Cylch yr Hengerdd, Oxford, May 20, 1978.
