Þórfinnr's military advances. For example, the thirteenth-century Orkneyinga saga states that, after Þórfinnr's consolidation of Orkney and Caithness—an action that likely took place after the death of his brother Brúsi—Þórfinnr was active in the Isles, parts of Galloway and Scotland, and even Dublin. The saga also reveals that Brúsi's son, Rǫgnvaldr, arrived in Orkney at a time when Þórfinnr was preoccupied with the after-effects of such campaigns, as it states that he was "much occupied" with men from the Isles and Ireland. Another source, Óláfs saga helga, preserved within the thirteenth-century saga-compilation Heimskringla, claims that Þórfinnr exerted power in Scotland and Ireland, and that he controlled a far-flung lordship which encompassed Orkney, Shetland, and the Hebrides. Further evidence of Þórfinnr's activities in the region may be preserved by Þórfinnsdrápa, composed by the contemporary Icelandic skald Arnórr Þórðarson, which declares that Þórfinnr raided throughout the Irish Sea region as far south as Dublin. It is possible that Knútr took other actions to contain Orkney. Evidence that Knútr installed Hákon as overlord of the Isles may be preserved by the twelfth-century Ágrip af Nóregskonungasǫgum. The historicity of this event is uncertain, however, and Hákon's authority in the Isles is not attested by any other source. Be that as it may, this twelfth-century text states that Hákon had been sent into the Isles by Óláfr, and that Hákon ruled the region for the rest of his life. The chronology outlined by this source suggests that Hákon left Norway at about the time Óláfr assumed the kingship in 1016. The former is certainly known to have been in Knútr's service soon afterwards in England. One possibility is that Knútr installed Hákon as overlord of Orkney and the Isles in about 1016/1017, before handing him possession of the Earldom of Worcester in about 1017. If this was the case, Hákon would have been responsible for not only a strategic part of the Anglo-Welsh frontier, but also accountable for the far-reaching sea-lanes that stretched from the Irish Sea region to Norway. It seems likely that Knútr was more concerned about Orkney and the Isles, and the security of the sea-lanes around Scotland, than surviving sources let on. Hákon's death at sea would have certainly been a cause of concern for Knútr's regime, and could have been directly responsible to the meeting between him and the three kings. If Hákon had indeed possessed overlordship of the Isles,