Theresa May was an authentically unionist prime minister. Rare was the speech that failed to mention her love for the four nations of the UK and she was of course a staunch opponent of Scottish independence.

Despite the rhetoric, though, May didn’t actually do much about it. Beset by Brexit and weighed down by the challenge of managing a split, fractious party in a hung parliament, she had little headspace or time to pursue policies that might strengthen rather than weaken the bonds of the United Kingdom.

Boris Johnson, I am told, is different. He wisecracks about the “awesome foursome” but is also determined to match words with action, ahead of next year’s Holyrood elections, which, depending on the result, could lead to a second independence referendum. If the SNP can be stopped from winning a pro-indy majority, and instead the pro-union parties win 65 or more of the Scottish parliament’s 129 seats, a referendum becomes much less likely.

The Prime Minister has set up a “Union Unit” in No 10, with the remit of developing policies and arguments that will persuade Scots to vote No in any future referendum. Discussions have been held with some of the Scottish Tory MPs who lost their seats in the recent general election about the role they might play engaging and listening north of the border. A report by Conservative peer Andrew Dunlop, a former Scotland Office adviser, looking at how the Union might be supported, is expected to be published this year.

“Theresa cared about the union, but there is a real sense of urgency under Boris,” says a UK government source. “There’s an awareness that Brexit has put a strain on the union and that action is required.”

The hint of a change of tactics and tone was seen at Prime Minister’s Questions this week, when Johnson responded aggressively to Ian Blackford’s standard complaint about Scotland being denied the right to hold a referendum. “Change the record,” the PM told the SNP’s Westminster leader.

Referring to Nicola Sturgeon as Alex Salmond’s “protegee” – the former first minister goes on trial in March over sexual assault allegations – Johnson accused the SNP of being “obsessed” with breaking up the UK, at the expense of Scotland’s public services. He also charged the Nats with inflicting higher taxes on Scots and warned the education system was in decline. “That is no fault of the pupils of Scotland, by the way, it’s the fault of the government of Scotland under the SNP, who are not giving them the chances they deserve because they are obsessed with breaking up the United Kingdom.”

This suggests the Tories see two weak spots where they might inflict damage on Sturgeon and her party. The first is the Salmond trial, which is potentially ruinous for the SNP’s reputation and inner harmony. The second is its record as a government – 13 years in, the performance of schools and the management of hospital projects are, in particular, giving cause for concern. Voters are starting to notice. And why shouldn’t the UK Prime Minister hold the Scottish First Minister to account? Why shouldn’t he publicly pick apart her flaws? It happens the other way around.

One can see from this how a campaign might be shaped to stop the Nats. The Salmond trial means this is already likely to be a difficult year for them. Can a smart, balanced unionist onslaught finally bring the high-flying SNP back to earth?

As well as aggressive politicking, the British government is expected to spend lavishly in Scotland over the coming period – strategists are currently looking at how to deploy cash in a way that doesn’t cross too blatantly into the devolved administration’s territory. The City Deals, which have given hundreds of millions of pounds to Scotland’s population centres, have established one precedent for action. A cash bung – in essence a bribe - would be an obvious way of showing that Scotland is a valued part of the UK and benefits from redistribution across the country.

There is also an awareness that the scare tactics of the 2014 referendum are unlikely to be quite so effective in a rerun. “Project Fear”, the nickname for the Better Together campaign, painted a lurid picture of the economic troubles an independent Scotland would face. It worked – just – but left a bad taste in the mouths of many. Government aides are working hard to create a new narrative of the Union for the 2020s, one which has a pull beyond pounds and pence and doomy warnings about IMF bailiffs.

There is also a view that Johnson’s unpopularity in Scotland is overstated. The PM has changed since winning his majority – he seems more serious, more aware of his responsibilities, more focused on uniting where there has recently been such bitter division. At his best, he is charismatic, clever and funny, and his advisers believe many Scots won’t necessarily be immune to those charms. We can expect a steady stream of cabinet-level appearances north of the border. There is an acknowledgement that Westminster has rarely felt so far from Edinburgh, and that this gap needs to be closed.

Of course, the SNP machine is one of the most formidable in the history of British politics. Sturgeon is a stellar electoral performer, and her party and government have an understanding of Scotland that can leave the British government looking flat-footed. The astonishing energy and belief that has taken the First Minister and her team through 13 years of government, elections and referendums, shows little sign of abating. For them, until independence is secured, the job can only ever be half done.

At last, though, there may be signs that the Unionist opposition is getting its act together. They’ve left it late, but the Brits aren’t going down without a fight.