Ok, I don't know about you but I never knew that the Orkney and Shetland Islands were ever the property of Norway. As it turns out, these islands saw an influx of Norwegians due to overpopulation (in comparison to arable land) in Norway during the first half of the 9th century. However, many of the Norwegians that came were Vikings. They decided to make the islands their buccaneering headquarters, killed off every male member of the the native Pictish population and set to the business of raiding and being Vikings.
By 875 the Norwegians had annexed both islands in the name of Harald Hårfagre the king of Norway. Over the next 5 or 6 centuries Orkney and Shetland would be christianized by Olav Tryggvasson and St. Magnus Cathedral was established. Essentially, things calmed down a bit.
In 1468, Orkney and Shetland were pledged by Christian I, in his capacity as king of Norway, as security against the payment of the dowry of his daughter Margaret, betrothed to James III of Scotland. The original deal also included that Christian I would receive 50k Rhenish guilders for Orkney and another 8k for Shetland. From that point on the islands have been under Scottish rule.
An interesting prologue--according to the original terms of the agreement, Norway had the right to redeem the islands for a fixed sum of 210 kg of gold or 2,310 kg of silver. Since the 18th century Norway has attempted to exercise that right several times but never with any success. In modern terms, the cost of redeeming the islands would be about USD $6.7 million in gold or a little over $1 million in silver. Either way, that's a heck of a deal for two islands. Maybe something for King Harald, or future King Haakon, to consider?