Is Alex Salmond really a Unionist?

I think he is. He wants to keep the pound, he wants Scotland's interest rates (and therefore economy) governed by the Bank of England, he wants free movement across Hadrian's Wall for Scotsmen and Scotswomen to live and work anywhere in the UK without being subjected to border controls, visas and work permits, he wants UK companies to invest in Scotland and employ its people. He wants to keep the Queen.

And yet he wants "independence". That is an interesting word in light of such enthusiastic Unionism. But it might mean more in an unwelcome way than Mr Salmond imagines. For if Scotland votes to leave the UK, it will be the UK's turn to decide what kind of relationship it wishes to have with Scotland. Perhaps there should be a referendum in the UK on this point. Scotland will have decided to be a foreign country from the point of view of the UK (like, say, Panama) and therefore the UK might ask itself about passport controls at the Border - a necessity when Scotland rejoins the EU, for passports must be shown when people enter the UK from elsewhere in the EU - and whether, if either the UK or Scotland does not remain part of the EU, Scottish nationals living in the UK will require Tier 2 work visas, and be required to leave the UK to return to Scotland if there are UK citizens who can do the jobs they currently hold.

These unpalatable consequences of the UK deciding that, as a foreign country, Scotland must be treated on the same basis as Panama and all other foreign countries, explains why Mr Salmond is a Unionist. Are Mr Salmond and his supporters honest about their Unionism?

I do not mention Panama lightly. Does anyone remember the Darien Scheme, Scotland's great venture of the 1690s in the isthmus of Panama, which was the proximate cause of Scotland's embracing the Union in 1707? Imagine the fate of the Royal Bank of Scotland recently if Scotland were not part of the UK, but a foreign country. Would the UK rescue a Panamanian bank? Would the RBS debacle not have been another Darien for Scotland, prompting it to understand why we are all better together when mutual help is required?

After the Darien disaster, the people of the geographical entity known as Great Britain got together, turning a small divided island into what proved to be a powerhouse. What was the result for Scotland? Well: look across the historical landscape from the Scottish Enlightenment and Edinburgh's New Town to the huge part played by Scots around the world as engineers, teachers, doctors, soldiers and statesmen, leaving a legacy from Canada to New Zealand, from India to South Africa to Australia. When the kingdoms united they did a lot more than when disunited.

There are two principal reasons why I share Mr Salmond's enthusiasm for the Union. One is that, like the majority of the people of the UK, I am conscious that we are literally inheritors of all its past. My mother's maiden name is Burns, her birthday is January 25. Tribalism and the ghastly divisive mythology of race and ethnicity do not merely fail to appeal to me, they do not even make sense.

Nor - and this is the second reason - does the equally ghastly, divisive and false ideology which springs from tribalism, namely nationalism. As an ideology, nationalism has a history as fertile as it is disgusting. It is about building walls. In this case it is about turning Hadrian's Wall into - well, let us hope not something too like the Berlin Wall. I do think the voters on September 18 will remember that, when they have cast their ballots, it will be the turn of the rest of the UK to decide whether, if Scotland chooses to be a foreign country, it should be accorded the same status as any other foreign country.

I shall regard it as a travesty if, to visit the land of some of my forebears, I have to get a visitor's visa from a Scottish Embassy in London, for that will be the symptom of a failure. Look across Europe at all those who would Balkanise the continent into fragments of division which once and so often plunged it into conflict - this being the aim of nationalists in Catalonia, Wallonia, Padania and elsewhere, to say nothing of the Eastern Ukraine: are these Scotland's bedfellows? A Scottish yes vote will give heart to those separatists, and the grand ideal of a unified Europe, with its rich shared heritage and its common purpose, will have been put into reverse.

Little actions can have very large consequences. When it is said that a yes vote on September 18 will be a one time only vote with huge significance and no way back, nothing less than the truth is being spoken.