Ælfgar evidently received considerable military aid from the Irish to form a fleet of eighteen ships, and together with Gruffudd ap Llywelyn, King of Gwynedd and Deheubarth invaded Herefordshire. Although this campaign ultimately secured Ælfgar's reinstatement, Ælfgar (then Earl of Mercia) was again exiled from England in 1058, and proceeded to ally himself with Gruffudd ap Llywelyn and a Norse fleet. Notwithstanding the fact that Scandinavian sources fail to report this operation, the Annals of Tigernach reveals that the leader of the fleet was Magnús, son of Haraldr Sigurðarson, King of Norway, and further reports that Magnús' forces were composed of Orcadians, Islesmen, and Dubliners. Exactly who Ælfgar received aid from in the Irish Sea region is uncertain. It is conceivable that, after his flight from England in 1055, Ælfgar was outfitted in Dublin, then ruled by Murchad (with Diarmait as overlord). Likewise, since Diarmait's forces had previously driven Echmarcach from Dublin in 1052, and apparently from Mann in 1061, the joint campaign of Ælfgar and Magnús in 1058—which utilised Islesmen and Dubliners—could well have involved Diarmait's cooperation as well. That being said, there are several reasons to doubt a part played by Diarmait in Ælfgar's military undertakings. For instance, Diarmait seems to have lent assistance to Ælfgar's enemies—the Godwinsons—in the 1050s and 1060s. Diarmait also appears to have previously backed Cynan ab Iago, a man who was a bitter rival and seemingly the eventual slayer of Ælfgar's ally and son-in-law, Gruffudd ap Llywelyn. Ælfgar's Irish confederate of 1055 is not identified in any source, and it is not clear that Diarmait had a part to play in the aforesaid events of that year. In fact, it is possible that Ælfgar received aid not from Diarmait, but from Donnchad—Diarmait's enemy and Echmarcach's associate—a man who then controlled the Norse-Gaelic enclaves of Limerick and possibly Waterford. Furthermore, although Diarmait appears to have gained overlordship of Mann by 1061, Echmarcach presumably enjoyed overlordship of at least part of the Hebrides in 1058. Since Magnús utilised Islesmen during his English campaign of that year, it is conceivable that Echmarcach may have played a prominent part in these operations. If Echmarcach was indeed involved in the campaign, the enmity between him and Diarmait could indicate that these two were unlikely to have cooperated as allies. The prime motivation behind Magnús' cooperation with Ælfgar is uncertain. One possibility is that he was attempting to establish