NICOLA Sturgeon has yet to make an announcement about the next independence referendum but the opposition parties already appear to be fighting against it. In London last night, both Ruth Davidson and Kezia Dugdale launched their first forays against the Nationalists, though there was no hint that they would be uniting in defence of the Union, as in 2014. “Better Untogether” looks like being the strap-line for the campaign.

Ms Dugdale, the Scottish Labour leader, called for a people’s constitutional convention to devise a new federal constitution for the UK. But weren’t we supposed to have had that after the last referendum? The former Labour prime minister, Gordon Brown, insisted that Britain was heading inexorably in a federal direction. If anything, the reverse has happened.

I don’t know why Ms Dugdale believes that this latest federal project has a better chance of success. Labour can’t do it on its own and the UK Government is occupied extricating Britain from the EU. The idea that Theresa May and the Brexiters will take time out to engage in a two-year constitutional talk-in is for the birds. It would anyway reopen the question of a federal Scotland having a different relationship to the EU than the rest of the UK, like Wallonia or the Faroes, and that’s something it’s determined to avoid.

Labour’s federal relaunch only confirmed how much has changed since last time. I used to be something of a believer in federalism but, eventually, you have to accept that the horse you are flogging has gone to meet its maker. No one is going to ask for that second question in the next referendum. Maximum devolution has gone the way of the DVD and VHS; no one is buying the machinery to make it play any more.

Ruth Davidson, the Scottish Tory leader, was having none of it. She rejected outright the Scottish Labour leader’s call for a new federalism. Instead, she claimed the Union was already changing to meet Scottish needs. She insisted, bizarrely, that the post-Brexit UK was a beacon of “free trade” and a bulwark against “economic nationalism”.

I don’t know if Ms Davidson has noticed, but Britain is about to leave the leading free trading zone in the world, the European single market. And the economic nationalists are firmly in charge at Westminster, thumbing their noses across the channel at those silly Europeans. It’s a bit rich to accuse the SNP of putting up economic borders when Mrs May is building a wall against our greatest trading partners.

Nor was there any mention in Ms Davidson’s speech of the raft of new powers – immigration, agriculture and fisheries, environment – we were told would devolve to Scotland after Brexit. This was a telling omission. Instead, she took the SNP to task for being preoccupied with the constitution instead of domestic issues such as education. Yet her government at Westminster is preoccupied with the greatest constitutional upheaval in 43 years.

Ms Davidson said Scotland leaving the UK as a response to Brexit was akin to “to stubbing your toe, to then amputate your foot”. I think this rather brutal imagery is telling. For we all know who is doing the amputation: it is the Conservative Government cutting Britain off from Europe. The Scottish Government is trying to cauterise the wound.

The problem for Unionists is that Ms Davidson will have to lead the next No campaign on her own. It’s going to be a tough gig, not least because she supported Remain. On this showing, she hasn’t got much to offer Scots except more hard Brexit.

But we’re getting ahead of ourselves. There has been no announcement yet of an independence referendum, even though everyone in Scotland is talking as if it’s already begun. The real arguments won’t start until the svelte lady sings. And Ms Sturgeon is still clearing her throat.