There was something slightly pathetic about Theresa May beetling up to Scotland in the hope of planting her legacy flag on the Union, before Boris Johnson and Jeremy Hunt got their hands on it. She wanted to get history's brownie points for having rejected a Scottish independence referendum in 2017. But saying no hardly counts as a triumph of statesmanship.

Actually, what she told Nicola Sturgeon in March 2017 was that “now is not the time” for Indyref2, which is rather softer than the hard line her would-be successors are taking. Now it's never. A flat no. Forget it. You'll have had your referendum.

Both Boris and Hunt made clear at the Perth Hustings that there will be no independence referendum, even if the SNP win outright in 2021. That's a sobering message for the independence movement, and for Nicola Sturgeon. She still regards the Section 30 route to a legally-binding referendum as the only plausible one. That is now road-blocked.

There has been a dramatic hardening of rhetoric against Scotland during this campaign. Theresa May came to Stirling to proclaim that Nicola Sturgeon “cannot be trusted”. That the Scottish government is incapable of negotiating “in good faith”. Why, Sturgeon had the temerity to portray the UK government's takeover of powers repatriated from Brussels as a “power grab”. You just can't deal with these people, May concluded.

We all know what Boris Johnson thinks about Scotland. A nation of “freeloaders”. He described Scotland having free care and free tuition as “pretty monstrous”. Jeremy Hunt has tended to be more emollient, but on Friday his gloves came off too. He condemned the Scottish Government as: “the most bullying, divisive, duplicitous, anti-business government Scotland has ever seen”.

Given that the Scottish National Party dominates the opinion polls, and has more seats in both parliaments than all the Unionist parties put together, this could be taken as an oblique criticism of the Scottish voter. I mean, are Scots so stupid that they don't realise they are being run by bullying charlatans? It's almost as if they can't be trusted to know their best interests, deluded as they are by the hypnotic rhetoric of separatism.

This was all rather redolent of how British imperialists, like Churchill, used to talk about nationalist leaders in the old British colonies. They were all wily demagogues, up to no good. Can't trust them as far as you can throw them. The subtext was: the only language they understand is firmness. Just tell them what the score is and let them get on with it.

This is very much the line taken in the Daily Telegraph last week by the Thatcherite former Scottish Secretary, Lord Forsyth of Drumlean. He says that the real threat to the Union comes from “giving in to Nationalists' demands”. The Tories best bet is to tell them politely but firmly that they can stick their independence up their Great Glen – or words to that effect.

All this is, of course, exactly what the SNP want to hear. There is nothing better for drumming up support for the Nationalist cause than hearing a phalanx of crusty Tory grandees telling Scotland to like the Union or lump it. Support for independence is creeping up – slowly but steadily – and is now 49% in the latest polls, and 53% if Boris Johnson wins.

True, demand for an early referendum on Scottish independence is certainly muted. But after Mr Johnson enters Number Ten – a racing certainty according to the latest YouGov poll – and a no deal Brexit looms, things could move fast. The SNP expect support for Yes, which has been stuck for five years, to jump dramatically. Possibly approaching that 60% which Nicola Sturgeon allowed the media to speculate back in 2015 was the threshold for calling a repeat referendum.

But it's going to be messy. There is already disquiet in the party and in the wider Yes movement at the SNP leader's apparent lack of enthusiasm for leading the independence revolution. But after this Tory leadership campaign, she can be in no doubt that there has been a sea-change in attitudes to Scotland from the governing party. No more Mr Nice Guy. Scots will have to learn to love Brexit Britain or take the high road out of the Union.

Yet, it's a little odd that Scotland should have become such a touchstone issue in the Tory leadership race. There are hardly any Tory members in Scotland, after all, and it is they who'll be doing the voting in the campaign, which is now reaching peak empty promise as the ballot papers go out. But both contenders seem to have chosen to make the Union and Scotland's place in it central to their respective campaigns.

They each claim, rather improbably, to have an almost religious attachment to the Union. It's blood-in-my-veins stuff for Hunt. The “most successful Union in history” according to Boris Johnson, clearly believing that the United States somehow fails to qualify as a union.

Perhaps this relates to something deep in the Conservative psyche: that Great Britain needs to retain its subject nationalities to prove that it is still a going concern. Certainly, the loss of Scotland - taking with it a third of the UK landmass, most of its hydrocarbons and all of its nuclear weapons - would be a devastating blow to Brexit Britain. The UK's prestige, already diminished as a result of the three years of chaos and indecision, would take an even greater knock. It could lose its place on the UN Security Council, become an empty chair at G7 Summits...

So, there was a bit of carrot to go along with the stick. Boris Johnson has declared himself “Minister for the Union” with the implication that devolution is now as important to the Prime Minister's role as First Lord of the Treasury . He is going to take Scotland well in hand, and ensure that all policies in future are 'stress tested' for compatibility with all four nations.

Jeremy Hunt too came bearing gifts. Scotland is to become a “green Silicon Valley”, a post-Brexit digital entrepôt. He presumably avoided saying “Silicon Glen” because that would have reminded Scottish voters of what happened the last time Scotland's future was predicated on new technology, back in the days when the Tory George Younger ran the Scottish Office.

At its height, in the early 1980s, Scotland's technology industry made one third of all the computers manufactured in Europe. Not any more. They went elsewhere as the UK de-industrialised under Margaret Thatcher. Mr Hunt also hyped his proposal to slash corporation tax to 12.5% - something Alex Salmond used to argue for. However, this is a policy for the UK as a whole, not Scotland, so there is no obvious comparative advantage, still less any promised to devolve business taxes.

But the headline message from both Tory candidates in the Perth hustings was withering contempt for the independence movement. This will no doubt please Conservative members in the southern shires, who have already largely given up on Scotland and regard the Union with pointed indifference. As YouGov discovered recently, the vast majority would willingly let Scotland go if it meant saving Brexit.

They may get their way sooner than they think.