Nobody, unless pure in heart to the point of saintliness or ingenuous to the point of gullibility, thinks that an invitation is always an unselfish offer of hospitality, or the expression of a genuine desire for more of the recipient’s company. All manner of calculation, and often hypocrisy or duplicity, goes into it.

We invite people to things because of their status, because we will look rude if we don’t, because other guests expect it, because we’re sure that they won’t come, and all sorts of other discreditable, or at least not completely sincere, reasons. That’s just family, social or work events; the politics of political invitations are, naturally, even more political.

It’s not usually as bluntly expressed as it was by the USSR’s Nikita Krushchev, who in the mid-1950s told Western diplomats: “If you don’t like us, don’t accept our invitations and don’t invite us to come to see you. Whether you like it or not, history is on our side. We will bury you.” Since, as it turns out, history was on the other side, and not only Comrade Krushchev but his system were buried, another form of invitation – the passive-aggressive – is now employed.

The First Minister gave a textbook example when she invited the Prime Minister to pop in and see her. It was a pretty piece of politics. Having waited until the day before his visit, when she’d already seen his packed schedule, she almost certainly knew he would refuse, and could then take umbrage and portray it as a snub. But if he had accepted, he would have been met with vocal protests, so she was bound to win either way.

Poor Sir Keir Starmer, up on the same day, didn’t – unless I missed it – even get the call to Bute House; as an expression of the negligible threat his party currently poses to the SNP, that may be more insulting than the trap dug for Boris Johnson.

This sort of manoeuvring is canny politics by Nicola Sturgeon, but it probably doesn’t do any more than confirm partisan voters in their opinions. It is, however – like the play within the play in Hamlet – a kind of enactment of the underlying issue that itself established and entrenched those stances.

For all three party leaders, that’s how to handle the question of a second independence referendum. The positions may seem obvious enough, but it is much less clear that those public declarations automatically correspond with the outcomes they want – or at any rate profess to want.

In the baldest formulations: the SNP have a manifesto commitment for a referendum within this parliament and, having been the most successful party and formed the government, say this constitutes a mandate. The Conservative riposte, so far, is that it does not necessarily constitute a mandate, that the legal powers are not within Holyrood’s gift, and that it’s too soon after a referendum that was supposed to be binding. Both parties’ stances are open to dispute, but seem straightforwardly confrontational.

The Labour position used to be harder to read, because the party’s support and potential support, like the party itself, is split, but Sir Keir’s interview the other day, in which he ruled out any deal with the SNP dependent on a referendum, seems to have solidified his stance.

But it is the least important. Labour doesn’t, on current showing, stand a chance of threatening the governing party north or south of the border, so Sir Keir’s not going to be in a position to “allow” a referendum. If things change markedly, he won’t need to, because he would have to have done very well against the SNP as well as overturning the Tories down south. The English arithmetic is not there without Scotland, and if he can’t do well here, he loses (forever) by accommodating the SNP, anyway.

The Tory position is fraught with difficulties, however blunt it looks. Even if you accept that there is no mandate for a second referendum, blank refusal feeds the sense that Westminster is impeding the will of Scots. It doesn’t matter whether you think that unfounded because it’s legally a non-devolved issue, or because the SNP does not (quite) have a majority of seats, let alone Scottish voters; it is a position that can only be held for so long, and the longer it is held, the more it encourages a narrative of obstruction.

The change in circumstances (notably Brexit) since the last vote undermines the idea that it’s too soon for another; that cannot remain a viable argument for very much longer, though those enthusiastic for another poll may well be mistaken about how widely the country shares their view. The more plausible delay argument, given lip service by all three leaders, is that the upheavals that the pandemic and recovery from it create are the priority.

Many SNP voters may be bursting for IndyRef2, and plenty others are critical of the party for not pushing harder for it. But there are also independence advocates who, like the Unionist leaders, think Now Is Not The Time (though they only say it privately). It would be a reckless SNP leader who didn’t ask: “But what if we lose?”

Rising support for independence may be as much a wish as a polling statistic; it’s certainly not clear-cut. Students of independence movements are acutely aware of the lesson of Quebec, when a second referendum 15 years after the first also fell short, seriously damaging the cause. Support for independence among young voters there is now under 30 per cent.

Similarly, Brexit may have convinced many that Scotland does not share UK priorities, but now that it has actually happened it demonstrates the disruption of hammering out terms, and – even if hoping to rejoin – doing so outside the EU.

Though some fanatics may have convinced themselves otherwise, any vote is far from won. If there were strong signs that the last result would be repeated, the Unionists’ best option, perversely, would be to accept it – an enormous risk. Ms Sturgeon’s, meanwhile, equally counter-intuitively, would be to hope for it to be vetoed by Westminster. It could end up that no leader wants it, or wants to veto it. But since IndyRef2 is a manifesto commitment, Covid may prove to be the only useful cover for getting out of it.