WHY did the former Tory Lord Chancellor, Michael Gove, suggest that Scotland could have control of immigration after Brexit? He envisaged a points-based system such as exists in Australia and Canada, where immigration controls are relaxed in sectors and regions that lack categories of workers.

It could be administered through the Scottish tax code that came into force last year.

So why has Theresa May apparently rejected it out of hand? Fear. The UK Government is afraid that, if it allows Scotland any latitude, it will be attacked by UK tabloid newspapers for allowing “back-door immigration” through Scotland. (Though the UK Government is still considering a scheme for the City of London, because, of course, money talks.)

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It’s a daft way to make policy but we live in daft times. Scotland needs EU migrants, indeed all migrants, for important demographic reasons, as Holyrood’s Europe committee reported yesterday.

We have an ageing population, a low birth rate and continued out-migration of skilled workers.

Only 15 years ago the population was at risk of falling below 5 million. This evoked images of a tumbleweed Scotland, denuded of people and economic activity.

In 2004, Labour First Minister Jack McConnell tried to stem the flow with the Fresh Talent initiative allowing students to remain in Scotland for two years after graduation.

But it was really free movement in the EU that solved Scotland’s population problem, as Poles and Lithuanians migrated here in large numbers after enlargement in 2004.

Scotland’s population is stable and the birth rate has increased because incoming families tend to have more children. So why, if there has been this huge increase in immigration over the last decade, has it not been a political issue in Scotland?

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If immigration has a downward impact on wages, as many critics of immigration claim, then surely this must have been happening here also. But mass migration hasn’t generated the kind of antagonism it has in England.

Is it that Scots are more tolerant of immigrants? Perhaps: Scotland’s biggest export has always been its people and, as a migrant nation ourselves, we’re possibly more understanding of the reasons why people move.

But the other reason is the issue that dare not speak its name: race.

In England, much inward migration was from Commonwealth countries and is much more visible than migration from Eastern Europe because of the colour of the migrants’ skins.

When people in England tell opinion polls that they “don’t feel as if they are living in the same country”, they often mean that city streets are filled with people who are obviously of a different race.

This is a problem for Brexiters. After Brexit, immigration won’t cease: half of migrants to the UK come from non-EU countries – around 180,000 a year.

This might increase to take up the slack from the fall in predominantly white immigration from EU countries.

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Paradoxically, Brexit could lead to more (visible) immigration in England rather than less.

But by then Scotland, if it remains in the UK, could be in a spiral of decline.

Non-EU migrants are reluctant to come here because of the weather and the lack of established BAME (black and minority ethnic) communities.

Scotland faces a double whammy: not enough workers and not enough tax revenues.

Unless Scots start breeding as never before, Mrs May’s immigration diktat could lead to tumbleweed Scotland becoming a reality.