Eyes roll in Downing Street whenever there is any suggestion the Prime Minister and the First Minister are, in some way, of equal status.
Hence why, in his letter, rejecting Nicola Sturgeon’s invitation for a cosy wee chat in Bute House this week, Boris suggested Michael Gove, his point-man on Scotland, was the person of the correct pay-grade she should be talking to.
When pressed on why he had refused the First Minister a one-to-one chat, the Prime Minister insisted – without a hint of irony – he was “always, always, always delighted” to meet Nicola. No-one, of course, believed him.
For her part, the First Minister said Boris’s rejection of her invitation had been “a bit strange” but she had not felt snubbed.
And yet, of course, it was a snub – with bells on.
Apart from the equivalence issue, No 10 wanted to avoid the appearance of the PM as a visiting foreign dignitary met by a gaggle of howling protesters.
Could his snub have had anything to do with how Nicola once again enraged him by signalling, 24 hours ahead of time, the official vaccinations committee would recommend all over-16s be offered a Covid vaccine?
In 2014, Theresa May, then home secretary, famously imagined a “future in which Scotland, Wales, Northern Ireland and England continue to flourish side-by-side as equal partners”.
It was a political phrase she probably regretted because, ever since, SNP chiefs have used it to batter Whitehall about how it has reneged on pursuing a partnership of equals.
However, given the Union is dominated by England, which has 10 times the population of Scotland, a promise of equivalence always seemed insincere. Has there ever been a family of nations, where the overwhelmingly larger member has not been seen as overweening by its smaller relatives?
From Downing Street’s viewpoint, Ms Sturgeon is the head of a devolved administration, while the PM is in charge of the Government that oversees the whole of the UK.
There is, of course, no love lost between the Prime Minister and the First Minister in what is a political hate-hate relationship.
Last year, when it was suggested Ms Sturgeon should have a pivotal role at the COP26 climate conference in Glasgow, a red mist quickly descended on Downing Street.
Boris spluttered, allegedly: “Over my f****** dead body. I’m not being driven out of Scotland by that bloody Wee Jimmy Krankie woman.”
Last summer when he first visited Bute House, just days after kissing the Queen’s hand, the newly-minted Prime Minister was met with loud protests; a mixture of anti-Brexit, anti-Union and anti-Boris.
Such was the kerfuffle in Charlotte Square the Prime Minister, after having his iced tea and antipathy with the FM, had to leave by the back door.
His last venture northwards came in January when more controversy was gently helped along by the FM, who made clear she was “not ecstatic” about the PM’s presence north of the Border and branded it, given the Covid travel restrictions at the time, non-essential.
Downing Street was incensed. It insisted how visiting different parts of the country to observe how they were battling the pandemic was a “fundamental” part of the PM’s role. It decried the view that this played into the idea of Scotland being a no-go area.
And yet, despite the PM’s assertion “wild horses” would not keep him from campaigning in Scotland ahead of the May Holyrood elections, he was nowhere to be seen because, privately, Scottish Tory colleagues were telling him to stay away as his presence would be electorally disadvantageous. And so, naturally, he did.
As for Cop26 in November, both the Prime Minister and First Minister know the last thing either of them wants is a political stramash ahead of the key international event, which would do neither of them any good and, more importantly, would not help galvanise the will needed to save the planet from a climate catastrophe bigger than the one already unfolding.
So, after last year’s Wee Jimmy Krankie outburst, it came as no surprise Boris would seek a more collegiate approach with Nicola, saying she would have a “huge role” at the summit but omitting to say what it would be.
And again he sought to underline the no-equivalence principle, declaring: “I hope very much the First Minister, along with all her colleagues around the UK, at whatever level in government, will evangelise, will exhort everybody that she represents and they represent to do the needful.”
But the biggest battle over equivalence will begin next year when, chances are, the constitutional clash over Scotland’s future will begin in earnest.
The Prime Minister knows the political deal the SNP is cooking up with the Scottish Greens will have as its main purpose a consolidated drive towards Indyref2 and making the case for independence.
As ever, the issue will generate maximum heat, if not light, at the Nationalist conference in September.
Sturgeon has already upped the ante by declaring her Government’s intention to hold its own referendum whatever the PM says. Boris has two options; ignore it or challenge it.
The first will lead to what the Unionists have branded a Catalan-style “wildcat poll”; the second a legal fight, which could end up at the UK Supreme Court.
Either way, Nicola will have succeeded in placing Scotland’s future in the headlines, hoping her argument wins the day: that a Holyrood democratic vote and the will of the Scottish Parliament have equivalence in their importance to a Westminster democratic vote and the will of the UK Parliament.
But to adapt George Orwell’s famous line in his allegorical novel Animal Farm: “All leaders are equal but some leaders are more equal than others.”