Boris Johnson is insouciantly reluctant to be seen travelling cap in hand to Berlin, Paris or Brussels in pursuit of new Brexit terms. He has not even bothered to make a phone call to the Irish taoiseach, Leo Varadkar, even though the Irish border is the crunch Brexit issue. His attitude to the European Union is to try to make the foreigners sweat, even if the result is a slump in the value of sterling, as it was on Monday. And yet, like Theresa May before him, Mr Johnson felt the need to go to Scotland at the very start of his prime ministership.

Why did he come? Why the exception? It is, after all, improbable that the prime minister will get a political dividend from his meetings in Edinburgh. The first, with the Scottish Conservative leader Ruth Davidson, was at best an exercise in damage limitation. Mr Johnson’s casual embrace of a possible no-deal Brexit (which he just as casually denied in an interview) has undermined both Ms Davidson and Tory credibility on the issue in Scotland. Meanwhile, although the brutal sacking of the former Scottish secretary, David Mundell, last week may not have received much attention in England, it has been widely seen in Scotland as an act that pulls the rug from under Ms Davidson.

The second meeting with the SNP leader and Scottish first minister, Nicola Sturgeon, was hardly any easier. Ms Sturgeon was evidently determined not to welcome Mr Johnson to Bute House with a smile. Inside, though, she must have been laughing. Mr Johnson embodies the kind of Englishness that grates most on nationalist sensibilities. He is often seen as a recruiting sergeant for the SNP. His visit provided Ms Sturgeon and her party’s formidable media operation with an ideal platform from which to promote their independence agenda in a way that is already gathering some momentum in the polls.

Very clearly, Mr Johnson came on what was otherwise likely to be an unrewarding visit because he could not afford not to. Scotland voted heavily to remain in the EU in 2016. Yet few in Westminster, particularly on the Tory benches, have ever taken the likely effect of Brexit on Scotland seriously. Mrs May came north in 2016 and said how much she loved the union, but she then went away and forgot about the issue. Mr Johnson, like most fervent leavers, never gives Scotland much thought either, any more than he bothers with Ireland. But it became shockingly clear during the leadership campaign that the Tory party is now full of people who simply do not care whether or not the UK remains together as long as they can have Brexit. Belatedly, even Mr Johnson now appears to get what is at stake, although he characteristically has no plan to address the issue.

This was embodied by the first part of Mr Johnson’s Scottish visit. His morning visit to the Faslane nuclear base on Monday can be explained in two ways. The first was that the security at Faslane ensured that he could give his press interviews against a strong visual backdrop without any interference from protesters. The second was that he was happier emphasising his commitment to the UK’s nuclear submarines and all they symbolise about Britain than in worrying about the signal that this gives to anti-nuclear opinion in Scotland. It was, in short, a visit aimed at the English audience rather than the Scottish one.

Mr Johnson made one important thing explicit in the interviews. Asked if he would rule out a second independence referendum in Scotland, he said the 2014 vote to stay in the UK had been “a once in a generation consultation” and that another vote would undermine trust in politics. That certainly sounded like a no, though it was not as clear as Mrs May’s rejection of the idea. It nevertheless throws down the gauntlet to the SNP, who have said that Brexit may justify a further independence referendum. This renews the possibility that Ms Sturgeon, despite having ruled out the possibility in March, may find herself having to reconsider a Catalan scenario, in which the Scottish government holds a referendum that is not legally binding and potentially illegal. That would be a fraught possibility, as events in Catalonia have shown only too obviously. But Mr Johnson would be reckless to assume that his own eagerness to leave the European Union will not encourage Scots – and others too – to abandon the British one.

• This article was amended on 30 July 2019. Text was added to clarify that Ms Sturgeon has previously addressed the possibility of a referendum not authorised in Westminster.