JUST what Scotland needs as the pandemic reaches a climax: a blond, tousled super-spreader coming north to infect us with a new variant of unionism. And possibly worse. SNP MPs like John Nicolson are condemning Boris Johnson for breaking his own Covid rules and visiting Scotland this week. It's worse than Dominic Cummings – at least he only went to Barnard Castle.

In reality, of course Nicola Sturgeon is gagging for the Prime Minister to come so she can show him her famous cold shoulder. Nothing is better for the independence cause than the beast from the south. Scots loathe Mr Johnson for being, well, so damned English. He sums up everything Scottish voters dislike about the public school-educated English elite.

So where will he go? It's much too cold to go camping in Applecross. Angry Nats in saltire masks will be waiting for him in the big cities. The Prime Minister can't even make his usual trip to the Brexit badlands of the north-east, where Scottish fishermen used to give him a safe haven. They're furious after the discovering that Brexit will not ban foreign trawlers from British waters for the next five years at least. And that Brussels is making life difficult for fish exporters. Well what did they expect? The EU is a protectionist alliance.

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So the PM might be better advised to spend his time speaking to his troops in Holyrood, where surprisingly the Tories remain the main opposition party. Though there is a small problem there too. Tory MSPs are led by his old adversary, Ruth Davidson, the kick-boxing baroness. The real leader of the Scottish Conservative Party is young Douglas Ross, a Westminster MP, who still looks like a boy come to do a woman's job.

Mr Johnson will just have to put some lead in his pencil. For there are dark clouds on the constitutional horizon. The battle for Europe is over; the battle for the Union is about to begin. Opinion polls show growing support for independence, not just in Scotland but in Wales and Northern Ireland. Is this Prime Minister about to preside over the break-up of Britain?

Actually, the current independence crisis is largely about the London media, lacking Brexit, having rediscovered Scotland and the SNP's lead in the polls. We've been living with this crisis for some time. But nationalism is never a real issue until the Sunday Times carries a front page warning about “Disunited Kingdom”, which, cough, just happens to be the name of my 2015 book on the last referendum.

In fact, the most recent poll shows a slight drop in support for Scottish independence. But the long term trend, established over 20 opinion polls, is a secure, though small, majority for independence. That is significant. Scotland is not growing any closer to the UK. However, I don't think that means there is going to be a referendum any time soon, no matter how many points Mike Russell puts on his indyref plan.

There is simply no way that Mr Johnson will concede a referendum on Scottish independence. I'll say it again. It is absurd to believe for one second that this Prime Minister would risk another referendum – not after what happened to David Cameron. He'll stick doggedly to his line that it's a “once a generation event”, which means, like the referendums on Europe, once every 40 years.

HeraldScotland: Boris Johnson will not be granting a second indepenedence referendumBoris Johnson will not be granting a second indepenedence referendum

Nor does it matter how big the SNP majority is after the Scottish Parliament elections in May. That cannot be regarded, in our constitution, as a de facto referendum – as Ms Sturgeon has herself conceded on many occasions. She will not declare UDI. Nor will she countenance a “wildcat” referendum, Catalan-style.

There has been much talk of the First Minister now backing a Plan B route to Indyref2 through a challenge in the courts. The idea is to pass a referendum bill (another one) and hope the UK Government takes the Scottish Government to court. Then, it is hoped, the justices of the Supreme Court will over-rule the PM, as they did over his prorogation of the Westminster Parliament, and affirm the Scotland's democratic right to self-determination.

Read more: One way or another, indyref2 is heading for the courts

I am reliably informed that the UK government's response to this is “bring it on”. There is not a snowball's chance in hell of the Supreme Court of the United Kingdom helping dissolve the UK. Plan B will likely turn into another legal paper chase ending up with the status quo: the 2017 Supreme Court ruling in the Miller case that Westminster is sovereign in all circumstances. Only a Commons vote could deliver a legal referendum through a Section 30 Order. That will not happen – not even Labour would vote for it.

So Plan B is at best an exercise in constitutional theatre. It may be useful propaganda. It may be better than doing nothing after the expected May landslide. But even if the Scottish Government mounts an “advisory” referendum, and even if Scotland's hard-pressed local councils agree to organise it, the result would have no constitutional significance. It could be attacked as an expensive vanity project. At best, a big opinion poll; at worst, if unionists boycott it, a costly embarrassment.

For independence to succeed, in the short term at least, the Scottish Government would need to mount a campaign to make Scotland ungovernable, either by insurrection or civil disobedience as happened in Ireland and colonies like India. The UK Government knows that this is not going to happen under the present leadership. Anyway, things are going pretty well for Ms Sturgeon right now, the Salmond affair aside. Why rock the boat? When the First Minister last tried to force Indyref2, in 2017, the SNP lost a third of its Westminster seats.

So Mr Johnson will take the hit this week, insisting that the relative success of the vaccination programme, and the extra pandemic cash, shows that the Union still delivers. This PM is used to being disliked, hated even, during the Brexit culture wars. His skin is thicker than rhinoceros hide and he will not give a damn.

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