Dyfnwal II of Strathclyde

Dyfnwal II (Gaelic: Domnall, English: "Donald") may have been ruler of the Kingdom of Strathclyde for some period in the early tenth century.
He is sometimes called Domnall mac Áeda (Mod. Gaelic: Domhnall mac Aoidh; Mod. English: Donald, Aodh's son), because of a passage in the Chronicle of the Kings of Alba. The passage reads "mortui sunt in tempore huius Doneualdus rex Britonniorum et Dunevaldus filius Ede elig7". It has usually been interpreted as "in the time [of Constantine II of Scotland, who reigned from 900 to 943] Domnall, king of the Britons died and Domnall mac Áeda was elected". The crux is the word elig7, usually interpreted as a shortening of eligitur (meaning elected). However, Benjamin Hudson has challenged this and argues that elig7 stands for Ailech, meaning that the passage is actually recording the death of Domnall mac Áeda, king of Ailech, known in other sources to have died in 915. However, from the 18th century, onwards through Skene in the 19th, and from the Andersons to Alan MacQuarrie in the 20th, eligitur has been the standard interpretation, and the passage is believed to indicate that Dyfnwal was the son of Áed and an otherwise unknown brother of Constantine II of Scotland (Causantín mac Áeda), whom Constantine made his tanist. However, more recently Dauvit Broun has taken up support of Hudson, and so consensus remains very much divided. The Oxford Dictionary of National Biography article by Broun on King Constantine II states 'It has been suggested that a King Dyfnwal of Strathclyde was his brother, but this is simply a misreading of an Irish source's obit of Domnall mac Áeda, king of the northern Uí Néill.'
Dyfnwal was once thought to have been the same ruler as Dyfnwal III of Strathclyde, and indeed this is possible. However, this is not generally believed, because of the time lag and because Symeon of Durham recorded that Owen I of Strathclyde, whom he calls "Ouuen, king of the Cumbrians", was defeated by king Æðelstan of England in 934. The latter puts the end of Dyfnwal's reign sometime before, perhaps a long time before, this year.\