As the Prime Minister made the case for preserving the Union to the Scottish Tory conference on Friday afternoon, BBC Radio 4 aired an engaging drama in which it had already been lost.

Dividing The Union by the young playwright James Graham (of recent This House fame) depicted David Cameron, bruised and pensive, heading north by train to thrash out the details of independence with an understandably chipper Alex Salmond.

The result had been close - just over 50% - but a win was a win. The melancholy Old Etonian plays golf with the Old Linlithgonian First Minister and eventually they cut a deal. It's an occasionally poignant play, and also a very believable one.

It was a scenario that would have made most of those present at the Scottish Conservative Party conference quake beneath their tweed or pinstripe exteriors, for Scottish Tories are primordial Unionists almost to a man and woman. The prospect of losing the Union to that beastly Alex Salmond - the very mention of whom makes them twitch - is simply too much to bear.

Which is why the Scottish Conservative and (although the conference banners omitted this bit) Unionist Party belatedly finds itself ahead of the curve on the constitutional question. Of course, in his speech the Prime Minister was at pains to emphasise this conversion to more powers wasn't opportunistic, "a consolation prize if Scotland votes No", but - to an extent - it is.

At the same time it represents the rediscovery of once natural Tory territory. For much of the 20th century the party was at the forefront of rethinking the Union and preaching what Ruth Davidson referred to yesterday afternoon as "constructive Conservatism" (a phrase borrowed from the shamefully neglected Scottish political thinker Noel Skelton). Even in 1999 figures such as Brian Monteith and Murdo Fraser were all arguing that a devolved parliament had to raise money as well as spend it.

Importantly, this thinking has progressed from the fringes of the party to its mainstream and, strikingly, previously sceptical figures such as Baroness Goldie and Ruth "Line In The Sand" Davidson are now completely on board. So, too, is the Prime Minister, not an irrelevant figure, given it might fall to him to devolve the powers in question. "Giving the Scottish Parliament greater responsibility for raising more of the money it spends," Mr Cameron said in his speech, "that's what Ruth believes - and I believe it too."

The media latched on to Mr Cameron's use of the word "can" in relation to granting more powers rather than "will" (on such semantics does the constitutional debate turn) but what the Scottish Sun dubbed "Davolution" is certainly sincere, something Ms Davidson rammed home yesterday afternoon: "We are 100% committed - from the Prime Minister down - to making sure that, after voting No, we deliver a settlement the people of Scotland want, within a union the people of Scotland want to keep."

In previous years, a legitimate charge against the Scottish Tory leadership was that its thinking was out of kilter with the party grassroots; just as Ted Heath's "Declaration of Perth" surprised the party in 1968, so too did this sudden conversion to fiscal responsibility. But strategists are keen to talk up a decisive shift in this respect too, tracing it back to a party meeting in Dunblane last November. The party, recalled one of those present, "surprised itself" in its willingness to embrace further devolution.

There is something in this. I recall watching Murdo Fraser joust with Lord Forsyth on the Calman proposals at a memorable Scottish Tory fringe meeting in 2010 and then four-fifths of the audience sided with Michael Forsyth against them. On Friday afternoon, by contrast, only one question to the Strathclyde commissioners was (politely) opposed to more powers.

The term insiders kept using was "sea change", but that overstates the case; it's truer to say that Tory activists are now less overtly hostile to the Scottish Parliament and further powers, but then progress is progress. Tellingly, when former Scottish Secretary Lord Lang told ITV his party should wait until after September 18 to discuss such things the story received very little traction.

In itself, however, backing more powers will not necessarily produce a Scottish Tory revival. Ms Davidson spoke of a devolution settlement "built on Conservative values" but, as the former Scottish Government policy chief Alex Bell pointed out last week, Unionists risk making the same mistake the SNP so often did, "that of banging on about powers without connecting them to any social purpose".

The Welsh Conservatives, not for the first time, are ahead of the curve on this, having recently endured a very public debate (resulting in several front-bench sackings) about the devolution of tax powers to the National Assembly and, more importantly, what they should be used for. They clearly want to pursue a tax-cutting agenda, and I suspect their Scottish counterparts do so too. How credible that is given the public spending climate is a moot point, but it might at least herald a return to non-constitutional political discourse, particularly if Labour (as recent reports suggest) moves in the opposite direction.

But it won't be easy. As More Scottish Than British, a lucid study of the 2011 Holyrood election by Chris Carman, Robert Johns and James Mitchell, points out, three years ago the SNP picked up more than one in five of those who'd voted Conservative in 2010 (including people who strongly identified as "British"), something the authors conclude "reinforces the impression that the party is confined to a rump of partisans with a fairly distinctive socio-demographic profile but unable to attract new voters to its ideas and programme". Ouch.

That said, this was the first Scottish Conservative gathering I can remember in quite a while where there were visible signs of political life. Ms Davidson made the best conference speech of her leadership, actually connecting with her audience, while usefully the venue, Edinburgh's shiny EICC, didn't conform to type by being dusty and half-empty. The independence referendum has undoubtedly fired up Tory activists; the challenge for the leadership is harnessing that energy and utilising it after September 18.

One of the most interesting figures to emerge from proceedings was the legal academic and Strathclyde commissioner Adam Tomkins. He politely suggested that Unionists had failed to make voters aware of the powers already possessed by the Scottish Parliament. Nevertheless he articulated clearly the case for adding more, but argued "what No means" was not only a Unionist matter but also "a pressing question for the Scottish Government and for the SNP".

In other words, Tories hope that as a result of their conference and, over the next few weeks, similar Labour and Liberal Democrat gatherings, on September 19 it will be Alex Salmond meeting David Cameron to negotiate a new devolution settlement and not the other way round as depicted so convincingly in Dividing The Union. The next six months will reveal if Unionists have left enough time to rewrite that particular script.