Arthgal ap Dyfnwal

Either he or his father, Dyfnwal ap Rhydderch, King of Alt Clut, may have reigned when the Britons are recorded to have burned the Pictish ecclesiastical site of Dunblane in 849.

After four months, the fortress fell to the Vikings, who are recorded to have transported a vast prey of British, Pictish, and English captives back to Ireland.

Two years after the fall of Alt Clut, Arthgal is recorded to have been assassinated at the behest of Causantín mac Cináeda, King of the Picts.

[11] The genealogy specifies that Arthgal was the son of Dyfnwal ap Rhydderch, King of Alt Clut,[12] an otherwise unknown ruler.

[17][note 2] The razing of Dunblane could be evidence that the British Kingdom of Alt Clut was in the process of extending its authority at the expense of the Pictish regime.

[21][note 3] The destruction of Alt Clut is also documented by Welsh sources such as the eleventh- to thirteenth-century Annales Cambriæ,[24] and the thirteenth- and fourteenth-century texts Brenhinedd y Saesson[25] and Brut y Tywysogyon.

[28] One possibility is that the Vikings had successfully secured control of the well that saddles Dumbarton Rock, thereby denying the Britons access to fresh water.

[40] On the other hand, the remarkable duration of the siege could indicate that, instead of merely plundering Arthgal's realm, Amlaíb and Ímar specifically sought and succeeded in capturing the capital.

[45] On one hand, the recorded ethnicity of the Vikings' captives could reveal that the Britons of Alt Clut possessed many English and Pictish slaves or subjects.

[44] The fact that the Fragmentary Annals of Ireland seems to show that Amlaíb promptly returned to Britain in about 872 could be evidence that the assault on Alt Clut was undertaken in the context of territorial conquest/control rather than the mere acquisition of portable wealth.

[68] One possibility is that Rhun had been exiled from his father's realm, and had been living at the Pictish royal court when Amlaíb and Ímar commenced their campaign.

[74][note 11] Although the site could have served as a Viking military base following the British defeat,[76] there is no archaeological evidence evincing its use as a seat of lordship until later centuries.

[88] Whilst it is possible that Arthgal met his end in Ireland at the hands of his Viking captors,[89] the title accorded to him on his death could be evidence that he had instead been ruling the new Kingdom of Strathclyde.

[92] For example, the twelfth-century Prophecy of Berchán attributes four victories to Causantín, with the fourth described as that of Cath Lures—a location possibly identical to Glasgow—where he overcame the "king of the Britons of the green mantles".

Map of Britain and Ireland
Locations relating to Arthgal's life and times.
Photograph of geological formation of Alt Clut
The fortress of Alt Clut occupied Alt Clut ("the rock of the Clyde"). [ 19 ] The mediaeval citadel that sat atop this geological formation formed the capital of the Kingdom of Alt Clut before it was captured and destroyed by Amlaíb and Ímar .
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The name and title of Arthgal's adversary Amlaíb as it appears on folio 25r Oxford Bodleian Library Rawlinson B 489. [ 38 ] The Viking kings of Dublin were accorded the Gaelic title rí Gall ("king of the Foreigners"). [ 39 ]
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The name of Causantín mac Cináeda , the brother-in-law of Arthgal's son, and the man who instigated Arthgal's death, as it appears on folio 29v of Paris Bibliothèque Nationale Latin 4126 (the Poppleton manuscript ): " Constantinus filius Kinet ". [ 55 ]
Black and white photograph of a mounted warrior inscribed upon a stone sarcophagus
A mounted warrior displayed upon the Govan sarcophagus. [ 71 ] This monument is perhaps the finest example of the so-called 'Govan School' of sculpture. The sarcophagus could to be that of Arthgal's adversary, Causantín. [ 72 ]
Black and white sketch of the banks of the River Clyde in the eighteenth century showing a hill upon the bank
An eighteenth-century engraving of the southern bank of the River Clyde at Govan . The scene shows a now-nonexistent artificial hill that could to have been the royal assembly site of the Kingdom of Strathclyde following the fall of Alt Clut. [ 83 ] [ note 12 ]