In 870, during the latter's reign, the fortress of Alt Clut was captured by Vikings, after which Arthgal and his family may have been amongst the mass of prisoners taken back to Ireland.

[12] In about 849, the ninth- to twelfth-century Chronicle of the Kings of Alba reports that Britons burned Dunblane, an ecclesiastical centre seated on the southern Pictish border.

[13] This attack took place during the reign of Cináed mac Ailpín, King of the Picts,[14] and may have been overseen by either Arthgal[15] or his father, Dyfnwal ap Rhydderch.

[16] The razing of Dunblane could be evidence that the Kingdom of Alt Clut was in the process of extending its authority at the expense of the Pictish regime.

[26] Another possibility is that Dún Guaire refers to one of two similarly-named sites in the Hebrides (on Mull and Islay),[27] In any event, the association of Rhun's wife with the fort could be evidence that she had been previously married.

[28] In 870, during the reign of Rhun's father, the fortress of Alt Clut was captured and destroyed by the insular Scandinavian kings Amlaíb and Ímar, following a naval blockade of four months.

[48] Arthgal's elimination may have been carried out in the context of an attempt by Causantín to capitalise upon the political turmoil wrought by the Viking onslaught.

[55] Although the Harleian pedigree identifies the listed rulers as those of the Kingdom of Alt Clut,[56] it is apparent that one aftereffect of the destruction of the eponymous fortress was that the capital of the realm shifted up the River Clyde to the vicinity of Govan[57] and Partick.

[65] Although it is possible that Arthgal ultimately met his end in Ireland at the hands of his Viking captors,[66] this title could instead be evidence that he had briefly ruled the new Kingdom of Strathclyde.

Whilst the first three victories are stated to have been won against Vikings, the fourth is described as that of Cath Lures—a location possibly identical to Glasgow—where he overcame the "king of the Britons of the green mantles".

If Rhun is indeed the prophecy's mantled monarch, his conflict with Causantín may have occurred in the aftermath of his father's demise, and may have been undertaken in an attempt to ensure his kingdom's independence from Pictish overlordship.

[71] If a garbled passage preserved by the Chronicle of the Kings of Alba is to be believed, Amlaíb was killed by Causantín in 872/874/875, whilst in the midst of extracting tribute from the Picts.

[75] Upon Ímar's death in 873, the Annals of Ulster styles him "king of the Northmen of all Ireland and Britain",[76] a title that may partly exemplify Viking overlordship of regions inhabited by the Picts, Strathclyde Britons, and the Welsh.

[77] In 875, seemingly during Rhun's reign,[78] the Chronicle of the Kings of Alba reports that the Picts suffered a devastating loss to insular Scandinavians at Dollar after which the invaders are said to have occupied the vicinity for one year.

[79] This Viking conquest—seemingly corroborated by the Annals of Ulster[80]—may be related to the campaigns of Hálfdan against the Picts and Strathclyde Britons in 875/876, as recorded by the ninth- to twelfth-century Anglo-Saxon Chronicle.

[81] This northern campaigning by Hálfdan could have been conducted in the context of the insular Scandinavians not only avenging Amlaíb's killing but of regaining Ímar's authority in the region.