Olaf the Black (Gilmore) & The Royal Norse House of the Isles
Godred Crovan, warlord of Islay and Man, forbade his enemies from building ships above a certain size, as these would then be war galleys and he would attack them.
Godred had a son called Olaf Bitling, whose daughter Ragnhild became the wife of Somerled, the powerful Norse Gaelic Lord of the Isles. Olaf also had a son, whom he named Godred after his father. This Godred was the father of Olaf Svarti (Olaf the Black), whose Gaelic name was Gillemuire . From this we get the modern Gilmore. Gillemuire is said to mean Devotee of Maire (or Mary).
Olaf Svarti / Gillemuire married Christina of Ross. A MacLeod genealogy mentions a Norse Gaelic king Arailt mac Semmair (Harald son of Sumarlidi), whose daughter Ealga Foltalain (Helga of the Beautiful hair) is said to be the mother of Gillemuire. The same genealogy claims Gillemuire as father of Leod (Ljotr), from whom the MacLeods take their name. Olaf is said to be the ancestor of the Morrisons.
The Chronicle of Man & the Isles charts the career of Gillemuire or Olaf the Black. As mentioned earlier, he took Christina of Ross as his wife. This was the daughter of Fearchar, Earl of Ross, whose help in quelling a northern uprising was rewarded with a knighthood by Alexander II King of Scots.
Alexander was keen to recover the islands under Norse rule, but Olaf gave his allegiance to Hakon, King of Norway. Olaf had originally ruled Lewis, but later moved to Man to share the rulership with his brother Ragnald. Ragnald had no wish to share, and with his ally Alan son of Roland, Lord of Galloway, planned to get rid of Olaf. Alan boasted that he would invade Norway and raised an army to attack Hakon's subjects in the isles.
Olaf left for Norway and informed King Hakon of the impending trouble. Hakon supplied him with a Norse fleet and Olaf returned to the isles, reaching Orkney first. After that he sailed to Skye and defeated the enemy there in battle.
At Islay the Norse forces attacked and slew many of those who had shifted their allegiance to King Alexander, commandeering eighty ships. They then sailed to Bute, besieged one of Alexander's castles there, captured it and seized considerable booty. A Scottish knight was ransomed for three hundred merks of silver, a respectable sum.
Olaf led the forces south after the death of his fellow commander Uspak. They landed in Man by way of Ulster and Olaf confronted Ragnald, who was killed. Olaf then became sole ruler of Man. Olaf died in 1237 after which Harald, his son, took over the kingship. The territories under his rule were Man, Lewis, Harris and Skye.
Unlike his father, Harald was less than enthusiastic about allying himself with the King of Norway, possibly due to the growing power of Alexander King of Scots. Harald was however summoned to pay homage in Norway and was kept there by the King of Norway for two years. He married the Norse king's natural daughter Cecilia, doubtless a move on Hakon's part to strengthen Harald's loyalty to him.
The Norwegian grip on the isles became weaker over the years largely due to the strong pressure exerted by Alexander II and his son Alexander III. At the time of Hakon's ill-fated expedition to the isles in 1263, Magnus, another of Olaf the Black's sons was King of Man.
Following the death of Hakon, King Alexander sent a force under Alan Durward and the Earls of Buchan and Mar to deal with Norse-Gaelic lords who had assisted Norway during the conflict.
Magnus, King of Man despatched warships against the invaders, but later became vassal of the King of Scots when Alexander prevailed. On the death of Magnus his Kingdom of Man was ruled by Alexander through a Norse-Gaelic lord Godfrey mac Mares.
Another son of Olaf the Black, Godred, invaded Man in 1274 to contest the rulership. Alexander responded by sending a fleet of ninety ships against him. Godred was invited to surrender but decided to fight it out instead, and on being routed, escaped to Wales.
The Kingdom of Man, Norse realm of Olaf the Black / Gillemuire, reverted to the Scottish Crown along with the Hebrides after the Treaty of Perth in 1266.