This brings a hollow laugh from Scottish Tories, who claim that the Brexiteers have seldom, if ever, evinced solid support for the Union of Scotland and England. Instead, they say that most of those who oppose the Prime Minister are determined to achieve a hard Brexit, where contact with the EU would be minimal, and that they’re using the Irish backstop issue as an excuse.

“I hope Theresa May gets the backstop issue sorted, if only to expose the fact that the Brexiteers are merely using it as a fig leaf to get what they really want – a Hard Brexit,” said one source.

While hope remains that Mrs May might yet be able to wring concessions from the EU to make her deal palatable, Scottish Tories are worried about what they say is “the rightwards direction of travel” of a large part of the English Tory party, as shown in the opposition to her Brexit negotiations.

She says she will stand down as Prime Minister before the next general election, due in 2022, but few believe she will stay in post that long, in which case the leadership campaign would then be fought out among the various Brexiteers who’d done so much to undermine her.

And of particular worry for Scottish Tory strategists is how that leader would be elected. “God help us if the leadership vote goes to the (English) members” – a clear reference to the perceived right wing nature of most Conservative members in England.

The Scottish Tory party has traditionally been seen as a more centrist party than its English counterpart – and won a majority of all Scottish seats in 1955 - but when it was perceived as moving to the right, especially under Margaret Thatcher, it gradually withered and almost perished – winning not a single Scottish constituency in the 1997 general election.

However, under Ruth Davidson’s leadership in the Scottish Parliament and David Mundell’s at Westminster, it has fought back in recent years to the extent that it is now the main opposition party at Holyrood and has 13 MPs in the Commons. Ms Davidson, now on maternity leave, has been especially successful in keeping her party firmly in the centre ground of politics and exploited the voters’ distaste for another independence referendum – still SNP leader Nicola Sturgeon’s main priority – even though Scotland, along with London, voted to stay in the EU.

Although a Remain supporter, Ms Davidson strongly supported Mrs May’s Brexit deal, especially in securing control of the seas off our coasts for the British fishing fleet, the bulk of which is based in the North East of Scotland, where the Tories captured several seats from the SNP.

It may seem a tall order but the Scottish Tories had harboured hopes of eclipsing the SNP and becoming the biggest party after the 2021 election to the Holyrood parliament. Now, however, a significant swing to the right by the national party could see them being hard-pressed to hold rather than gain seats.

As well as generally lining up behind Theresa May the Scottish Tories also secured the overwhelming support of the bulk of Scottish business and industry for the PM’s compromise deal.

Under Ms Davidson the Tories in Scotland had killed the ghost of Margaret Thatcher and were perfectly able to portray themselves as a middle of the road party. That said, the Brexit shambles and the fears of a No Deal, Hard Brexit or even a second EU referendum has revived SNP fortunes, despite its high taxation and poor education policies, and means that Nicola Sturgeon has regained her swagger.

A lurch to the right would give her a major boost and cause major problems for the maintenance of the Union.