Whilst attempting to return to the Isles in the autumn of 1248, the newly-wed's ship was lost at sea south of Shetland in a tidal race known as Sumburgh Roost.

The chaos brought about by Haraldr's demise appears to have contributed to the invasion of Argyll, and near conquest of the Hebrides, by Alexander II, King of Scotland.

[14] Haraldr reigned during an apparent lull in an ongoing and vicious struggle over the kingship fought between two rival branches of the Crovan dynasty.

[24] Haraldr also ruled during a period of competing claims to the overlordship of the Isles,[26] a region comprising the Hebrides and Mann, known in the Norse world as Suðreyjar (the "Southern Islands") due to its geographical position in relation to Norway itself.

[28] In fact, on several occasions during the reigns of Haraldr's royal predecessors, leading Islesmen sought recognition and protection from Norwegian monarchs.

[26] Meanwhile, Henry III, King of England also had an interest in the Isles, and worked to bring the Crovan dynasty closer under the orbit of the English Crown.

The chronicle states that a friend of Haraldr had been slain in the uprising quelled by Lochlann, possibly indicate that the latter fled in fear of the king.

[42] In fact, a transaction between Llywelyn ap Gruffudd and Ralph de Mortimer that concerns the lands of Maelienydd and Gwerthrynion, and appears to date to 1241, makes note of a witness named "Godredo filio regis Mannie".

[45] If the chronicle is in error in its account of the maritime demise of Guðrøðr Óláfsson, and he is indeed identical to the like-named Manx prince on record in Wales, his activities outside the kingdom of his forefathers may have been a consequence of the troubles following the Haraldr's accession.

[46] The chronicle's account of the flight to Wales may, therefore, reveal that Lochlann tried and failed to replace Haraldr with an otherwise unknown younger son of Óláfr.

Hákon's delegates in the Isles—a certain Gospatric, and Giolla Críost mac Muircheartaigh—are described by the chronicle to have seized control of the island, and taken tribute which was due to the Norwegian king.

[57][note 4] About a decade before, when Haraldr's father first gained complete control of the kingdom, Óláfr journeyed to Norway and may have rendered homage to Hákon.

[63] Although Haraldr attempted to oust Hákon's representatives on several occasions, his successive invasions of Mann from the Hebrides ultimately proved unsuccessful, and the chronicle indicates that he finally journeyed to Norway to render his submission.

The source reveals that the boundaries of his kingdom were carefully defined by Hákon as the islands which had been previously ruled by Haraldr's father, his uncle (Rǫgnvaldr Guðrøðarson), and his paternal grandfather.

[47] Upon his return to the Isles, the chronicle states that the Manxmen rejoiced at his arrival; and declares that he afterwards reigned quietly and peacefully, enjoying an alliance of friendship with both the English and Scottish Crowns.

[65] The earliest member of the Crovan dynasty known to have utilised a seal is Haraldr's paternal grandfather, who attached such a device to a confirmation charter granted in about 1154.

[72] One of Haraldr's charters to which a seal was attached was a grant to the monks of Furness Abbey concerning mining rights on Mann, the use of a depot at "Bakenaldwath" (probably Ronaldsway), and the freedom from tolls and customs.

[83] Similarly, the thirteenth-century Chronica majora reports that Henry confirmed the honour of knighthood upon Haraldr on Easter day that year.

[85] According to the seventeenth-century antiquarians William Camden and John Selden, this title appeared on the legend of seals borne by the dynasty.

[98] The compilers of the chronicle clearly considered the union to have elevated Haraldr's prestige above that of his predecessors,[47] as this source claims that Hákon had declared he would hold his new son-in-law "in great glory and exalt the throne of his kingdom above all who ruled before him in the Isles".

[107] An alliance with a ruler of the Isles would have certainly benefited Henry's ongoing military operations in Ireland,[108] and it is possible that it was such a pact that had prompted Mac Somhairle's involvement against the English.

[106] In 1248, the Chronicle of Mann, Hákonar saga Hákonarsonar, and the Icelandic annals indicate that Haraldr and Cecilía drowned whilst voyaging from Norway to the Isles.

[123] The maritime disaster in which Haraldr and Cecilía lost their lives demonstrates some of the difficulties faced by the Norwegian Crown in maintaining control of the far-flung Norse colonies west over sea.

[31][note 12] Not only did the calamity deprive the Islesmen of a capable king, but cost the Norwegian Crown a closely connected advocate in the region.

[132] According to Hákonar saga Hákonarsonar, Alexander had made it clear that he had no intention of turning back until he had acquired control of the western Norwegian dominions within his sights.

[133] Within about two decades, such desires would be fully realised by his successor-son, with the final eclipse of Norwegian overlordship in the Isles and the extinction of the Crovan dynasty itself.