Then again, it comes ill from the Labour Party to denounce Mr Johnson for his comments. They introduced devolution in 1997 with the expressed aim of killing off separatism for good. The governance of Scotland and the electoral system were both designed to stop a single party (ie the Scottish National Party) from ever taking power alone.
It is not the Tories who have supercharged independence over the years but Labour. It was the party of the Scottish establishment. It held more than 50 of the country’s Westminster seats. Labour, in partnership with the Lib Dems, formed the first post-devolution government and made enough of a pig’s ear of it to play into the hands of the nationalists.
First under Alex Salmond and now under Nicola Sturgeon, the SNP has consolidated power in Scotland even after the crushing defeat in the 2014 independence referendum. That was supposed to be a “once in a generation” stab at separatism, an argument that Mr Johnson often deploys in telling the Scots there won’t be another.
But that was before Brexit which was always going to be problematic, to say the least, if England voted to leave the EU and Scotland voted to remain; and so it has proved. In 2016, more than 60 per cent of Scots voted to stay. The SNP narrative that the country was being removed from Europe against its will by English voters and a Westminster parliament has been hard to gainsay ever since.
If there is a trade deal and Scotland as part of the UK can benefit from both that and from the wider opportunities offered by Brexit, the wind will be taken out of Miss Sturgeon’s sails. She will probably still win a majority at the Holyrood elections next May and will still demand an independence referendum which Mr Johnson will still try to deny her. But in the circumstances of an EU trade deal, the SNP will find it hard to win that referendum and Boris would be well advised to allow a Section 30 order under which a plebiscite can legally be held and call their bluff.
The expectation at Westminster is that there will be an agreement with the EU and that the current stand-off with Brussels represents last-minute brinkmanship before the deed is done. Indeed, some senior Conservatives believe that, with Dominic Cummings out of the way, a deal is now a certainty because the downside for Mr Johnson of not securing one is too great.
It has even been reported that Lord Frost, the UK’s chief negotiator, believes the shape of a deal will be apparent by this time next week. But since the sticking points of fishing and state aid remain the stumbling blocks, one side or the other or both will have to give some ground. There is still a chance, therefore, that a refusal in London or Brussels to cross red lines could scupper the talks and the UK will leave the transition period next month on World Trade Organisation terms. If that happens then the Union will be in peril.
You can imagine how this will play in Scotland where a succession of opinion polls has shown a majority for independence. Hard-line Brexiteers will doubtless say “who cares?” and insist that the country will be able to go it alone quite happily on WTO terms, which may be true.