If Ruth Davidson weren’t on maternity leave, it’s tempting to believe the former Territorial Army Signaller would by now have commandeered a tank and be rumbling down the M6 with the gun pointed firmly in the direction of the ERG. Davidson’s contempt for Boris Johnson and his cohorts is absolute and withering. Her no-nonsense, pragmatic Conservatism does not allow for the preening self-indulgence of the Tory far-right.

But Davidson is with baby Finn, and this has left something of a hole in the Brexit debate, at both a Scottish and UK level. The leader of Scotland’s Tories broke her silence this week when she took to Twitter to praise Theresa May’s “cojones of steel” and pledge her full support for the PM ahead of the confidence vote, but otherwise her voice has been conspicuously, if understandably, absent.

This doesn’t mean the Scottish Conservatives are dormant, or that Project Ruth is in abeyance. The party at Holyrood remains fully signed up to Davidson’s liberal, One Nation stance. And if there isn’t a tank on its way to London, there are certainly a few rhetorical exocets being fired. “When I look at what’s going on down south, I feel appalled and embarrassed,” one prominent MSP tells me. “I hate the English party. I’m horrified at the support for no deal being expressed by party members. I’ve stopped reading ConservativeHome.”

If this sounds like a temporary huff, the fault lines run deeper. Senior Scottish Tories believe the UK is on a trajectory to crash out of the EU without a deal, and that this could be fatal for the unity of the United Kingdom. I understand that they will back any measure that prevents no deal, and could publicly express support for a second referendum – if May’s deal can’t pass parliament – as early as next week. I’m told both Davidson and her stand-in Jackson Carlaw are signed up to this position. “No deal would be disastrous and jeopardise the union so we will reluctantly have to go back to the country and ask them,” says a source.

The Scottish Tories would potentially favour a two-question referendum, along the lines of 1) Do you want to leave the European Union or remain on existing terms?, and 2) If you want to leave should we do so on the basis of the deal that has been agreed or leave without a deal?

There is tremendous anger that the party at Holyrood has been placed in this position, for a number of reasons. One is that support for a second EU referendum will make it much harder to argue against a second independence referendum in a few years’ time. “We would have to accept if there is a pro-indy majority after the 2021 [Holyrood] election there will be a second referendum,” says a source. On the upside, this would allow Davidson to frame the campaign as a binary choice between more constitutional disruption from the SNP or allowing the new UK settlement to bed down with the Conservatives.

The travails of Brexit have fractured the previous unity of the Scottish party. The group of MPs at Westminster were once seen as being loyal to Davidson, and to owe their seats to her popularity, but some have split away either to speak out against May’s deal or to support the more extreme end of the ERG position. “Project Ruth feels very much like a Holyrood project now,” says an MSP.

This may well have disruptive long-term consequences. Scottish sources say that if the UK party elects an English nationalist leader – ie someone from within the ERG group – it would strain the bonds to breaking point. It would also undermine the 2021 campaign – “if the Westminster Tories are as divisive and newsworthy at that point then it doesn’t matter what we do, we’re fucked,” according to a key member of Team Davidson.

This, in turn, could lead to a formal breach, with the Scottish party choosing to break the link with the UK party and become independent. “An increasing number of people at the top table think we need our independence,” says a senior MSP. The belief is that while Davidson would be unlikely to drive the split, she will leave the party in such a position that her successor will do so.

It remains unclear whether Brexit will destroy the integrity of the UK. But it will be a tremendous irony if one of the first institutions to fall apart under its strain is the Conservative Party itself.