My old friend Kenny Farquharson of the Times hit the nail on the head the other day when he tweeted: “There is a flaw in the SNP’s ‘let’s concentrate on the EU single market and ignore the UK single market’ schtick. Nobody is buying it.”

Indeed, the SNP approach on Brexit has a hole in it. Ever since the June 23rd referendum on Brexit the party’s leadership has emphasised the need for Scotland to stay within the EU Single Market. That’s not just an attempt to continue to have access to the EU Single Market (which all manner of countries do, it’s a question of what the terms are). Nicola Sturgeon and her ministers want to stay inside the Single Market even though the rest of the UK looks set to leave under Brexit.

It is a curious position that owes more to the SNP’s obsession with independence and its habit of virtue-signalling than anything else. The thinking runs appears to run like this: the EU is nice, the Single Market is nice, the UK is not nice, so let’s like good and virtuos types stick with what’s nice, even if a majority of Scots want to stay part of the UK.

But the SNP government position ignores that another another single market is far more important to the Scottish economy than the EU. Scotland is in a highly successful single market, with free movement, a banking union, shared currency, excellent cultural and linguistic ties, and a great deal of trade. It is called the United Kingdom. Which the SNP wants to leave.

The figures on trade are worth restating, and getting put on a t-shirt if you like that sort of thing. According to the Scottish Government’s own figures, Scotland exports £11.6bn to the EU, £15.2bn to the rest of the world and £48.5bn (64% of exports) to the rest of the UK.

The EU Single Market is the least important component of Scottish exports. The UK is the most important. Yet the SNP policy is to put up barriers with its biggest trading partner in favour of its smallest trading partner. That is not, to put it mildly, a sensible idea.

For those interested, the background on the creation of what became the EU Single Market – and the semi-comical role of Thatcher and Arthur Cockfield, the cabinet minister she sent to Brussels who went native – is in my new book.