Today the Prime and First Ministers will meet for the next stage of the great, endless – nay relentless – constitutional tango.

As things stand, the deadlock will continue: Theresa May will insist that Brexit means Brexit while Nicola Sturgeon will counter that Remain means Remain. Neither of them, however, can adequately flesh out those meaningless soundbites.

But there’s also an intellectual impasse. I wrote last week that for all independence has been talked up since 24 June, the associated case for Scotland going it alone still hasn’t been updated. Sure, there’s an SNP “Growth Commission”, but all the other evidence suggests that Sturgeon et al will fight a second referendum on the same quixotic basis as before.

Read more: Theresa May warned imposing Brexit settlement on Scotland could break up Britain

Unionists, meanwhile, are faring little better. Speaking ahead of today’s meeting, Mrs May once again stressed the “importance of our great Union”. “Far more than mere geography brings us together,” she added, “and we are much more than the sum of our parts.”

As Donald Trump would say, these were just words, or rather just the usual hackneyed lines. Naturally the Prime Minister has lots on her mind, but if Ms Sturgeon is failing in the obvious task of making the independence case more realistic and compelling, then Mrs May is also neglecting her side of the argument.

And meanwhile that (once) “great Union” of which she spoke suffers death by a thousand cuts. Although the 2014 referendum kept Scotland part of the UK the fact the question had been put at all arguably weakened the Union, while the 2015 general election, in which the Tories weaponised the prospect of the SNP holding the balance of power, undermined it even more. And Brexit, well Brexit was but another large nail in its coffin.

Heroically, Mrs May continues to try and frame this in positive terms, saying in her statement that as we move into “this new chapter” (of what must be a pretty bad book), Scotland and the UK had to “seize the opportunities ahead”, achieving “far more together than we could ever do apart”. I couldn’t even get to the end of that sentence without rolling my eyes.

For the theoretical opportunities aren’t altogether clear given the state of the pound and recent reports that banks big and small are preparing to shift parts of their operations outside the UK. It sounds as unrealistic as the hopelessly optimistic visions of an independent Scotland conjured up by the Nationalists a few years ago, based on little more than assertion and wishful thinking.

Read more: Theresa May warned imposing Brexit settlement on Scotland could break up Britain

And when it comes to inter-governmental relations, all the Prime Minister could offer was something faintly patronising about today marking the beginning of “a new grown-up relationship” between the UK Government and the devolved administrations. This provoked a tired-and-emotional outburst from former First Minister Alex Salmond that rather illustrated May’s point, but again it was accompanied by the sound of hammering.

The First Minister, of course, intends to provide the nails. Her ongoing determination to set Westminster up to fail on a number of fronts might be the usual cynical posturing, but it also happens to be highly effective. On his recent visit to Scotland David Davis rejected the First Minister’s demand to devolve immigration, as the SNP knew he would. But it allows the Scottish Government to appear reasonable and the Tories intransigent, as will be the case again if Mrs May attaches conditions to the Section 30 Order necessary for another referendum to take place.

As I said, it’s death by a thousand cuts. Ms Sturgeon can present herself as having fought, fought and fought again to find a way of keeping Scotland in both the EU and the UK, only to be thwarted by the wicked Tories. Unionists, meanwhile, will be left mouthing platitudes, tired old lines about Scotland and the UK being “better together” and pointing out, self-consciously of course, that the numbers still don’t add up for independence.

But that doesn’t matter as much as it once did. The “Leave” vote in June demonstrated that appeals to economic self-interest are subject to the law of diminishing returns, even if they happen to be true. What resonates more, as I’ve written many times before, is the existence of a compelling narrative. And although the independence proposition is full of sizeable holes, the SNP have still managed to tell a much better story about Scotland outside the UK than any Unionist has about Scotland remaining inside it.

Read more: Theresa May warned imposing Brexit settlement on Scotland could break up Britain

And more to the point, no one’s even trying. The last, and in fact only comprehensive, attempt to fashion an intellectual defence of the UK came from the pen of Gordon Brown a few months before the 2014 referendum. The former Prime Minister realised the need to look forward rather than back, which is why he opted for a quasi-federal vision of a more autonomous Scotland inside a radically redrawn United Kingdom, but his was a lone voice.

It was also more than two years ago, and subsequently few convincing defenders of the Union have emerged to lead and create a narrative of what it could be, particularly in the wake of the European referendum. Scottish Tory leader Ruth Davidson had a reasonably good stab before that, but Brexit makes it considerably harder. As the journalist Alex Massie has observed, the caricature of the UK perpetrated by some Nationalists as a UKIP-style, xenophobic post-imperial relic now looks rather more accurate.

The Daily Telegraph, meanwhile, reinforces that caricature by campaigning for a “modern-day” £120 million version of HMY Britannia, which it believes will “help secure trade deals” once the UK formally leaves the European Union at some point in 2019. This is so far out that it’s been rubbished by a UK Government minister citing boring old facts, but it probably won’t make any difference; the 1950s nostalgia trip will continue.

There is, to be fair, an outfit called “Scotland in Union” which aims to unite people “around a positive view of Scotland in the UK” and assist then “in taking action”, although again it’s not altogether clear what that “positive view” is, nor what action can be taken to promote it. Simply pleading for a return to the good old days when Scottish politics didn’t revolve around political posturing and constitutional naval-gazing won’t cut it, Unionists have to beat the SNP at their own game.

Interviewed yesterday, Scottish Labour leader Kezia Dugdale underscored this point. Asserting that “most Scots” want to “be part of both unions”, she proceeded to offer a scant defence of the Union beyond pointing out (rightly) the “sad reality” that the difference between “what Scotland raises in taxes and what it spends is £15 billion”. That sort of argument was fine two years ago, but where will it stand once support for independence starts creeping past the 50 per cent mark? If Unionists are serious about preserving the UK, they’d better start developing some better dance moves.