Alan later played a considerable part in Alexander II, King of Scotland's northern English ambitions during the violent aftermath of John's rejection of Magna Carta.

Alan's involvement in the Isles, a region under nominal Norwegian authority, provoked a massive military response by Hákon Hákonarson, King of Norway, causing a severe crisis for the Scottish crown.

As ruler of the semi-autonomous Lordship of Galloway, Alan was courted by the Scottish and English kings for his remarkable military might, and was noted in Norse saga-accounts as one of the greatest warriors of his time.

[44] The fifteenth-century historian Walter Bower echoed this statement, adding that Alan obtained a lordship of one hundred sixty knights' fees, and took an oath on William's behalf to uphold the treaty.

In 1211, Ross and Moray, the northern peripheries of the Scottish realm, were invaded by Gofraid mac Domnaill, a member of the Meic Uilleim, a kindred that contested the kingship.

[50][note 6] Facing continued opposition early in 1212, William likely undertook the treaty negotiations at Norham as a means of retaining good relations with John, and the agreement itself was likely concluded in the context of shared security concerns.

The successful implementation of Alan's massive grant in Ulster, therefore, would have not only served English interests in the region, but would have also dramatically increased the security of the Scottish realm.

In effect, the alliance between John and Alan appears to have been a coordinated campaign constructed by the English and Scottish crowns in an effort to secure the control of outlying territories where their royal authority was disputed.

[61][note 8] In July 1212, John summoned Alan to send one thousand of the "best and most vigorous" Gallovidian troops to assist the English forces in a planned campaign directed at northern Wales.

[82] Midway through June, John was forced to accept the terms of his opponents, and so confirmed the charter of liberties known as Magna Carta, a concession that led most of the rebel barons to renew their pledges of homage to him.

[87] By the end of June, Alan was confirmed in his Irish lands, whilst Thomas received custody of the castle of Antrim, and was granted an Ulster lordship centred at Coleraine.

In 1216, for instance, Alan was identified as a rebel in arms by an English government memorandum,[82] and the Chronicle of Melrose reports that Gallovidians formed part of the Scottish army that invaded Northumberland in July 1217.

[90][note 13] Furthermore, when the English ordered Alexander to hand over custody of the castle of Carlisle in September 1217, Alan's name was also included in the correspondence directed at the Scots.

[95] Although these particular lands laid within Westmorland, and had been granted by John to Robert de Vieuxpont in 1203, Alan's Morville ancestors had held the district as late as 1173, giving him a claim to the region.

For instance, in about 1219 his clerk was indicted for unlawfully drawing revenues in Penrith,[100] and in 1223 Robert de Vieuxpont was still having difficulty regaining possession of lands that Alan had confirmed to John of Newbiggin.

Contributing factors to Alan's tardiness in English affairs were likely the death of his mother in June 1217,[102] and his subsequent succession to the Morville inheritance of Lauderdale and Cunningham, substantial territorial blocks within the Scottish realm.

[120] Both this source and the Orygynale Cronykil of Scotland by Andrew Wyntoun, reveal that Alexander's troops mounted a second and successful assault the following year, resulting in the region's submission.

As the first quarter of the thirteenth century began to wane, contentions between the half-brothers broke out into outright war,[149] and Alan is recorded aiding Ragnall against Amlaíb Dub.

Of the two, Ragnall appears to have been the most palatable to the Scots,[151] and may have been a key player in Scottish plans to counter the threat of the Meic Uilleim, and their probable Ulster supporters, the Uí Néill.

[169] Although the chronicle's description of the attack alludes to Gallovidian involvement, as it states that the expedition originated from Galloway, the fact that Ragnall commanded only five ships suggests that this support may have been waning.

[171] The lack of substantial Gallovidan support in Ragnall's final foray may have been due to a flare-up of insurrection in Scotland that required Alan's immediate attention as constable of the realm.

[174] Although Alan's marital alliance with Ragnall had likely been welcomed by the Scottish crown, the fact that the two were unable to quickly deal with Amlaíb Dub caused serious repercussions.

[181] Specifically, the saga singles out the aforementioned sons of Dubgall mac Somairle as "unfaithful" to the Norwegian king,[182] and several versions of the source describe Alan as the "greatest warrior at that time", possessing a large force of men and ships with which he plundered throughout the Hebrides.

[193] Meanwhile, news of the gathering Norse fleet reached Alexander, who appears to have made straight for the western coast, diverting his attention to the now rapidly developing crisis.

[194] It was probably June when the Norse fleet finally rounded Kintyre, entered the Firth of Clyde, and made landfall on Bute, where Óspakr's forces stormed and captured the castle of Rothesay.

There the Norwegians overwintered before returning for home in 1231,[204] and following the death of Ragnall's illegitimate son Gofraid Donn, King of the Isles the same year, Amlaíb Dub regained complete control of the island kingdom.

[176] In fact, the Norse had not been intent on solely restoring order in the Isles, but had directed their retaliatory campaign squarely at Scottish-held territories, thereby endangering the recent westward advances of the Scottish crown.

[18] On the other hand, the husbands of Alan's daughters were prominent men of Anglo-Norman descent, and the prospect of bringing about the demise of the semi-autonomous lordship, through its division between such eminent Englishmen, was an advantageous opportunity that Alexander could not pass up.

[266] One of the Scots who played a key part in the king's destruction of the Gallovidian resistance was Ferchar mac in tSagairt, Earl of Ross, a rising star in Alexander's administration, who happened to be Amlaíb Dub's father-in-law.

[283] As the lord of Renfrew, North Kyle and Bute, and allied in marriage to the nearby earls of Carrick and Lennox, the steward was the most powerful Scottish magnate in the Clyde region after Alan.