Arthgal map Dumnagual
King of Strathclyde (816-872)
It was during the reign of Arthgal that the political map of the north changed irrevocably. His contemporary was Kenneth mac Alpin
king of the Scots and Picts (840-858); the man traditionally credited with finally uniting the kingdoms of Dal Riada and Pictavia under one ruler.
Perhaps it was in an attempt to forestall the threat of this new political union that in 849 Arthgal took advantage of the recent death of Kenneth mac Alpin and raided and burnt Dunblane. In any event Arthgal seems to have successfully defended the independence of the kingdom until
around 870 when the fortress of Alt Cluid was stormed and taken by the Viking Olaf, king of Dublin. (With the assistance and support of Constantine I, king of the Scots, no doubt.)
Arthgal himself was taken prisoner and shipped to Dublin awaiting ransom. The ransom was never paid, and it was there that he was murdered, either at the instigation of Constantine I or of Arthgal's own son Rhun.