Charter evidence dating to the early 1260s reveals that Dubhghall resigned the Clann Suibhne lordship into the hands of Walter Stewart, Earl of Menteith.

The fact that some members of Clann Suibhne were unwilling to subject themselves to Stewart domination is evinced by the record of Murchadh supporting the cause of Hákon Hákonarson, King of Norway, who led a retaliatory campaign to reassert Norwegian authority in 1263.

[57] Thus provoked, Hákon assembled an enormous fleet—described by the Icelandic annals as the largest force to have ever set sail from Norway[58]—to reassert Norwegian sovereignty along the north and west coasts of Scotland.

[59][note 7] The fact that members of Clann Suibhne were unwilling to subject themselves to Stewart domination is evidenced by the record of Murchadh supporting the Norwegian cause.

[37] In July 1263, the armada disembarked from Norway, and by mid August, Hákon reaffirmed his overlordship in Shetland and Orkney, forced the submission of Caithness, and arrived in the Hebrides.

[65] The saga, and pieces of poetry embedded within it, glorifies the subsequent ravaging of Kintyre, suggesting that it was this rapaciousness that finally compelled Aonghus Mór and Murchadh to come into the king's peace.

Certainly the saga reveals that these west-coast magnates duly submitted to Hákon, swearing oaths of allegiance, surrendering hostages into his keeping, and delivering the island of Islay into his control.

The king is further said to have levied a tax of one thousand head of cattle upon the Kintyre headland, and a particular fortress[67]—most likely Dunaverty Castle[68]—is stated to have been surrendered to Hákon by an unidentified knight.

[80][note 9] Military actions conducted by Ailéan are specifically acclaimed by the saga, which states that he took several hundred head of cattle, and caused much destruction throughout Scotland.

Whilst Dubhghall and Ailéan were awarded the forfeited island territories of Eóghan Mac Dubhghaill, a certain Ruðri received Bute, and Murchadh was granted Arran.

[92] Not only did Hákon fail to break Scottish power, but Alexander III seized the initiative the following year, and oversaw a series of invasions into the Isles and northern Scotland.

Recognising this dramatic shift in royal authority, Magnús Óláfsson submitted to Alexander III within the year,[93] and in so doing, symbolised the complete collapse of Norwegian sovereignty in the Isles.

Specifically, with the conclusion of the Treaty of Perth in 1266, Hákon's son and successor, Magnús Hákonarson, King of Norway, formally resigned all rights to Mann and the islands on the western coast of Scotland.

[95] As a result of this evaporation of Norwegian sovereignty, there is reason to suspect that families like Clann Suibhne were increasingly venerable to retaliation at the hands of the Scottish Crown.

[101] Evidence from the Scottish exchequer, concerning Uilleam's reception of monetary aid for commanding two hundred serjeants on behalf of the king in the Hebrides, also validates these accounts.

[102] Further evidence of a concerted campaign against Hákon's supporters is the record of Walter Stewart assembling a royal fleet at Ayr,[103] and of Uilleam taking twenty head of cattle from Kintyre.

[104][note 11] In the wake of the Norwegian withdrawal, and the violent extension of Scottish royal authority into the Isles, Aonghus Mór[106] and Murchadh had no choice but to submit to the Scots, and were forced to hand over their sons for their good behaviour.

[126] These accounts locate his capture in the Owles, a territory around Clew Bay, and state that he was handed over to the earl by the local lord, Domhnall Iorrius mac Maghnusa Ó Conchobhair,[127] a man otherwise known to have been closely aligned with the English in Ireland.

[129][note 13] A particular piece of contemporary Gaelic poetry, composed by Giolla Brighde Mac Con Midhe, appears to reveal that Clann Suibhne was closely allied with the Uí Domhnaill.

[138] As with Clann Suibhne, Magnús became a target of Scottish aggression in the 1260s, and appears to have earlier formed a pact with a powerful Irish family to strengthen his position.