AT a time when Scotland needs to be united more than ever before, up pops a hoary old chestnut to cause some worry for people who are perhaps unaware of the history of the two archipelagos off our northern coast.

Ever since the discovery of North Sea oil, there have been regular suggestions that Shetland might go its own petroleum-financed way but now it is the turn of Orkney to be in the spotlight.

The suggestion that Orkney might secede from the United Kingdom and join Norway grabbed all the headlines, and the idea that Orkney could become a Crown dependency like the Channel Islands or the Isle of Man is not as daft as it sounds – though UK Government policy is not to allow any more such dependencies.

But what it’s really all about is gaining more power for the islands’ local council and a bigger share of the funds distributed by central government, there being no doubt that Orkney is the poor relation of our island authorities. Yet one reader was so concerned that he e-mailed me to ask if I could shed some light on why Orcadians could even consider transferring to Norway. After all, it was the Orkney Council leader, James Stockan, who mentioned Norway.

The simple answer to that question is that for centuries, Orkney was indeed part of Norway and the islands were the southern part of a kingdom which at times included Denmark and Sweden.

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Famously home to some of the oldest settlements in Europe dating back 5000 years, Orkney was in the hands of the Picts when the islands were invaded by the Vikings in the eighth century. The Norsemen made it their base for raids to the Hebrides and west coast, and some of the Vikings stayed to become farmers. The Norwegian governing system of jarls (earls) was introduced and Norwegian control over Orkney and Shetland was soon the de facto reality, recognised by various Scottish monarchs.

In 1106, Magnus Erlendsson became Earl of Orkney but he was assassinated by his own cousin who disputed the earldom. A Christian holy man, Magnus was soon acclaimed as a saint and St Magnus Cathedral in Kirkwall is dedicated to him.

In 1263, King Haakon IV of Norway led a campaign of war from Orkney down the west coast but was defeated by the Scots at the Battle of Largs and died on the return trip to Orkney. His successor as King of Norway, Magnus VI, negotiated a peace deal with Scotland’s King Alexander III which became the Treaty of Perth of 1266. The Treaty recognised Norway’s rights over Orkney, and in return the Isle of Man and the Hebrides became part of the Scottish kingdom with the Scots having to pay an annual sum to Norway.

Henry Sinclair, or St Clair, was a Scot who was made Earl of Orkney and it was he who supposedly led an expedition to the unknown lands across the Atlantic, landing in Newfoundland around 1398. Thus it could be argued that Norsemen and Scots from Orkney really discovered the continent of America nearly a century before Columbus.

By coincidence, tomorrow is the 554th anniversary of the event which ultimately led to Orkney and Shetland becoming part of Scotland. On July 10, 1469, King James III of Scotland married a Nordic princess, Margaret of Denmark. She is always known as Margaret of Denmark, and indeed she was born in Copenhagen, but at the time of her birth, her father King Christian I also ruled over Norway and Sweden, the three countries forming the Kalmar Union. He would later lose Sweden, but only after his daughter married the King of Scotland.

King Christian and his Kalmar Union was in a poor state financially when negotiations took place over the vital matter of Margaret’s dowry. It is recorded that discussions between Scotland and Norway about the possible marriage had started when Margaret was just four.

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There was a complex background to the marriage which was very much a dynastic arrangement suggested by Charles VII, king of Scotland’s ancient ally France. Scotland had not paid the sums due for the Hebrides and Isle of Man, and Christian I badly needed the money. But he was persuaded to marry Margaret to James and cancel the Scottish debt.

James III was just 18 when he married 13-year-old Margaret, whose dowry was secured on Orkney and Shetland. Christian failed to pay James III, and so the islands became Scottish and have been so since 1472 when the Scottish Parliament passed an Act formally annexing them.

Council leader Stockan was not wrong when he told the BBC: “We’ve been part of the northern kingdom for much longer than we’ve been part of the UK.”

He cannot deny, however, that Orkney has been Scottish for about as long as it was Norwegian. The Norse influence on the islands can be seen everywhere, and for several centuries local people spoke a distinct language known as Norn. The last native speaker of Norn died in 1850, and various words of Norn survive in ceremonial language on the islands as well as in the names of ships.

Is there any chance of Orkney becoming part of Norway? The UK Government has said a flat “no” and the Scottish Government has instead offered talks on improving the governance of the islands which is politician-speak for “we’ll bung them a few more quid”.

But I think the definitive answer comes from Norway. The Guardian was told by Øivind Bratberg, a senior lecturer in political science at University of Oslo, that Stockan’s ideas were “entertaining” but a non-starter, not least because Norway has no system of crown dependencies.

Bratberg said: “There’s no model the Orkney Islands could lay claim to that would allow them to actually become part of Norway. They could affiliate themselves more, certainly – cultural ties could be intensified, there could be festivals … But politically, constitutionally, in terms of international law, I’m afraid it’s a non-starter.”