Thorfinn next claimed two trithings of Orkney from his nephew Ragnvald, who demurred to giving up what the Norse king had conferred on him, but, finding he could not cope with Thorfinn’s Orkney, Caithness and Scottish forces, Ragnvald fled to King Magnus, who gave him a force of picked men, and bade Kalf Arnason also to help him, although Kalf was Thorfinn’s friend, and near connection by marriage.

The two jarls met in battle in the Pentland Firth, off Rautharbiorg or Rattar Brough in Caithness, east of Dunnet Head, Kalf Arnason with his six ships standing out of the fight.  Thorfinn had sixty ships, smaller, and, save Thorfinn’s own, lower in the waist than those of his enemy, who thus easily boarded them, and then attacked Thorfinn.  Surrounded and boarded on both sides, Thorfinn cut his ship free and rowed to land.  Arrived there, he removed his seventy dead, and all his wounded.  Next he persuaded Kalf Arnason to join him with his six ships, and renewed and won the fight, though Ragnvald himself escaped to Norway.[18]

Sailing thence in 1046 with one ship and a picked crew, Ragnvald surrounded Thorfinn,[19] who was wintering in Mainland of Orkney, and set fire to the Hall at Orphir in which he was, but the earl tore out a panel at the back, and, escaping through it with his young wife Ingibjorg in his arms, rowed in the dark over to Caithness, where he remained in hiding among his friends, all in Orkney believing him dead.  Ragnvald then seized all the islands, and lived at Kirkwall.

But, while Ragnvald was in Little Papey—­now Papa Stronsay—­to fetch malt for Yuletide, Thorfinn returned, and surrounded the house in which Ragnvald was, by night; and, on his escaping by leaping through the besiegers in priestly disguise, Thorfinn’s men followed him, and, led by his lapdog’s barking, discovered him among the rocks by the sea, where Thorkel Fostri slew him, Thorfinn meanwhile annihilating his following, save one man.  This man, who like the rest, was one of King Magnus’ bodyguard, he bade go to his king and tell the tale, and he seized Kirkwall by stratagem.  Jarl Ragnvald is said to have been a man of large stature and great strength, and to have been buried in Papa Westray, but a grave nearly eight feet long, that would fit him, has been found where he fell in Papa Stronsay.

All this left Thorfinn with his great aim achieved.  He was now sole jarl of Orkney and Shetland, and sole earl of Caithness and Sutherland, and he also held Ross and the western islands and coast down to Galloway, and part of Ireland, as his rikis or conquered tributary lands.

The fourth and last period of his career now begins with his dramatic visit to King Magnus in Norway; and, on the death of that king, he became the friend of his successor, Harald Hardrada, in 1047, and after visiting King Sweyn in Denmark, and Henry III, Emperor of Germany, rode south to Rome probably in 1050 along with, it is said, his cousin Macbeth, king, and a good king, of Scotland, returning thence to Orkney to his Hall at Birsay at the north-west corner of Mainland.  Thorfinn went to the Pope not only for absolution, but to get Thorolf appointed bishop in Orkney, according to Adam of Bremen, c. 243.