page_title: Arthgal ap Dyfnwal
section_title: King of Alt Clut
hierarchical_section_title: Arthgal ap Dyfnwal / King of Alt Clut
caption_attribution_description: English: Photograph of Dumbarton Castle taken on 27 July 2006.
context_page_description: Arthgal ap Dyfnwal was a ninth-century King of Alt Clut. He descended from a long line of rulers of the British Kingdom of Alt Clut. 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.
  In 870, the seat of Arthgal's realm—the island fortress of Alt Clut—was besieged by the Viking kings Amlaíb and Ímar. 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. The fall of Alt Clut marked a watershed in the history of Arthgal's realm. Afterwards, the capital of the kingdom appears to have relocated up the River Clyde to the vicinity of Govan and Partick, and became known as the Kingdom of Strathclyde.
  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. The circumstances surrounding Arthgal's death are uncertain. Whilst it is possible he was captured by the Vikings in 870 and slain whilst still in captivity, it is also possible that he was reigning as king when he died.
context_section_description: In 870, the fifteenth- to sixteenth-century Annals of Ulster, and the eleventh-century Fragmentary Annals of Ireland reveal that the insular Scandinavian kings Amlaíb and Ímar laid siege to Alt Clut, and succeeded in capturing the fortress after a blockade of four months. The destruction of Alt Clut is also documented by Welsh sources such as the eleventh- to thirteenth-century Annales Cambriæ, and the thirteenth- and fourteenth-century texts Brenhinedd y Saesson and Brut y Tywysogyon. The fact that such far-off sources make note of the event may exemplify the alarm caused by the Vikings' successes throughout Britain. According to Fragmentary Annals of Ireland, Alt Clut only fell to attacks after the well went dry. 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.
  The following year, the twelfth-century Chronicon Scotorum, the Annals of Ulster, and the Fragmentary Annals of Ireland reveal that Amlaíb and Ímar returned to Ireland with a fleet of two hundred ships, and a mass of captives identified as English, British, and Pictish. The exportation of these people to Ireland is also attested by Annales Xantenses, a ninth-century German source. The captives could have been meant for ransom, or may have been intended for the Dublin slave market. It is possible that Arthgal and his family were amongst those imprisoned.
  The reasons behind the attack are uncertain. On one hand, it is possible that Alt Clut was targeted because it was regarded as a rich target. 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. It could be that Amlaíb and Ímar regarded the kings of Alt Clut as an active threat to their maritime interests, and that the fortress of Alt Clut served the Britons much like how longphuirt were utilised as naval bases by the Vikings in Ireland. The destruction of the citadel may have allowed the Vikings to gain unrestricted access into central Scotland. 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. On the other hand, the recorded ethnicities may be evidence that Alt Clut's fall was the only recorded incident in what may have been a series of coeval Viking campaigns in the region, and may indicate that Amlaíb and Ímar not only established overlordship over the Strathclyde British, but that they also asserted power over the English of Lothian and throughout the Pictish realm. Although it is possible that the Scandinavians sought a connecting route between Dublin and York, the fact that there are no waterways or suitable portages that bridge the Firth of Clyde and the Firth of Forth may well be evidence against this. 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.
caption: 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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