In No. 10, two conclusions were drawn: that they had a mole (perhaps on Sage) and that the Labour party’s policy was to try to look prescient. The conclusion? Ignore it. In such times, they reasoned, no one cares about Westminster games. But it’s a different matter when it comes to being upstaged by Nicola Sturgeon.

To many Tories, she is the real opposition leader these days. If Boris Johnson’s premiership collapses — despite delivering Brexit and even if he sees off Covid — it will likely be due to her. Until the pandemic, opinion polls showed little change in appetite for Scottish independence. But since then, support for separation has surged.

It’s not that the Scottish government has managed the crisis well — an Imperial College study found that Scotland along with England had among the highest rates of death from all causes in the first wave of the pandemic — but politically, Sturgeon’s handling has been deft. She has not established a Boris-esque pattern of making promises that are later abandoned.

So when she called for a national lockdown this week, few were surprised that Johnson did the same within hours. As a general rule in this pandemic, when Sturgeon takes an action, it’s not too long before Johnson follows. She even hinted at this herself, telling MSPs that while she wouldn’t dare to predict what the Prime Minister would say in his address on Monday evening, she suspected it would ‘not be dissimilar to here’.

She has developed a reputation for being consistent while Johnson has one for being on the backfoot. Even among English voters, her approval ratings trump his.

‘It’s one thing after another,’ complains a Scot Tory. ‘Nicola gets in before him and is consistent in what she says — Boris says one thing then does another.’ The manner in which the new lockdown has been handled is a case in point. Johnson said on Andrew Marr that parents should send their children to primary schools, only to announce the closure of all schools 24 hours later.

There are those in the Conservative party who are concerned that this is a precursor to how things will play out after Covid. Even if the Prime Minister succeeds in achieving ‘a sort of terminus’ of restrictions by 5 April, Easter Monday, his Scotland battle will still only be beginning. Sturgeon is forecast to win a majority in Holyrood in May, and on a pledge (she will argue a mandate) to have a second referendum. No one expects the Prime Minister to grant such a request, but any refusal needs to be done with care.

A denial risks landing badly with swing voters, and could increase support for the SNP. ‘If we keep saying “no” it just allows Sturgeon to beat us over the head — especially if there is an indicative vote,’ says a government adviser, pointing to the possibility of the SNP staging a Catalan-style non-binding referendum as a form of protest.

Tory MPs are worried. Michael Gove has been leading much of the response in government, but a policy committee on the union is also being set up on the backbenches. ‘There is a complete acceptance that we are going to have to do something,’ says an MP involved.

The Tory hope is that the polls are changeable — that the rise in support for independence is not sturdy. They also hope that the Brexit deal will take the heat out of the question, although Tories grumble that not enough thought went into how to promote it in Scotland. ‘But it was a rare time Nicola was off kilter,’ says a Tory MP. ‘They escalated the horrors of no deal so much that just getting a deal seemed OK, no matter what wasn’t or was in it.’ The next wish is that Covid will be defeated — and so Sturgeon’s daily televised briefings, which Conservatives see as party-political broadcasts on behalf of the Nationalists, will finally end.

But that leads on to an issue that No. 10 isn’t keen to discuss: personalities. Tories will privately admit that Johnson is the SNP’s greatest weapon: they want to frame the debate as Nicola vs Boris. The Prime Minister’s unpopularity in Scotland is such a sensitive topic that in the past those close to him have even regarded ministers who talk about the importance of the union with suspicion: are they bringing up the issue to damage Johnson’s leadership, rather than because they really care about it?

As one minister puts it, were Johnson and Sturgeon to ‘fall off a cliff’ and new leaders take over, it could be a very different situation. Rishi Sunak is viewed by Tory strategists as the cabinet minister with the best appeal, outranking both Starmer and Gordon Brown among Scottish swing voters.

Johnson’s supporters hope that a delay to a referendum would not only give unionists time to ‘reset the dial’ but also expose divisions in the SNP. One senior minister takes the view that any wait would be more damaging to Sturgeon than Johnson: ‘They have been promising a referendum for years and eventually will just look weak’ if one does not happen.

There are plenty of SNP members working on the assumption that there will be a referendum this year if not next. Should that fail to materialise, Sturgeon will come under new internal pressure to deliver on it by any means necessary.

So far she has been reluctant to suggest anything as drastic as a protest referendum. Those around her are acutely aware that the idea would scare off precisely the middle Scotland voters that the independence cause needs to win over. But the more radical figures in her party back the idea, and will grow louder if nothing else materialises.

The Prime Minister knows that to lose Scotland would be a resigning matter. And there’s a chance he wouldn’t even be allowed to get that far: his party might not keep a leader who looked close to losing the union. To avoid this becoming a bigger issue, Johnson needs to find a way of breaking the pattern that has developed — and getting one step ahead of Sturgeon. The future of the union, and his premiership, depends on it.