"WHO is Jackson Carlaw?” ran a BBC website headline yesterday, several days after he’d resigned. Scottish Tory leaders are so obscure that people need reminded of who they are even when they depart.

One suspects that the same fate may await his successor, Douglas Ross, as he is installed tomorrow following last week’s coup. The MP for Moray has even less public profile than Mr Carlaw, who at least was known for selling cars.

You wonder how long the party can survive this before it lapses into historical irrelevance. Of course, the Scottish Tory Party will always be kept alive by its umbilical relationship with the UK Conservatives. A relationship which is both its salvation and its curse.

Murdo Fraser MSP, the former deputy Tory leader, wisely realised this after the 2014 referendum and proposed a breakaway Scottish party, like the Canadian Liberals or the Bavarian CDU. But it ain’t gonna happen – certainly not under Mr Ross, who appears to want to continue banging away at the old dead Union themes.

That no one is listening should be evident to everyone who looks at the opinion polls or talks to Scottish voters. A line has been crossed since Brexit. The Union as it is now is no longer viable. It has become a focus of discontent as Scotland is shoe-horned into a new UK internal market replacing the EU single market.

There is another way. Over the past couple of years there has been talk in Unionist circles of a new Act of Union to cement the new post-Brexit relationship. The Prime Minister is thought to be interested in something dramatic that would redefine relationships in this “awesome foursome”, as he calls Britain.

The unionist columnist Stephen Daisley put flesh on the bones in an article this week. This new Act of Union would, in his model, restore the sovereignty of Westminster in a unitary UK state. It would define what the powers of the Scottish Parliament are, instead of leaving them open-ended as is the case in the 1998 Scotland Act.

“Bring it on,” says Nicola Sturgeon. On the face of it, this would seem like the ultimate power grab – abandoning all pretence that the Scottish Parliament is anything other than a talking shop, a unit of local government, Strathclyde Region writ large.

And yet, there could be something in this New Union idea if turned upside down and used to recognise not subordination, but Scottish autonomy. It could even come in the form of a new Treaty of Union, as in 1707, to embrace a new constitutional reality.

Such a treaty would recognise that Scotland and England still want to be part of Great Britain, as it also said in 1707. But it would start from the premise that Scotland is a country in its own right. That Scotland voluntarily relinquished its sovereignty in 1707, but now intends to run its own affairs in a new legal partnership.

This New Union would recognise that Scotland’s Parliament exercises entrenched constitutional powers: something that was promised in the post-“Vow” Scotland Act in 2016, but wasn’t delivered, as the Supreme Court ruled in 2017.

This New Union would be regarded by diehard unionist (and Scottish nationalists) as a capitulation: not so much an Act of Union as an Act of Disunion. However, it could also be the creation of a new Union of equals – one that draws on the past but recognises changed realities.

Like the European Union, this Union would be a legally-binding partnership of nominally independent countries. It would be defined by a commitment to common economic, social and environmental objectives, free movement, human rights, common trading standards, mutual defence and a common currency.

Giving Holyrood full economic powers, including tax and borrowing, but within the confines of a common currency, would keep Scotland within the tent, much as countries like Slovakia and Slovenia are within the European Union. They are both sovereign countries, but their currency is the euro, they obey the Maastricht stability rules on debt and accept Brussels’ right to regulate trade and negotiate treaties on their behalf.

Scotland would be in charge of most of its own affairs, but would remain part of a United Kingdom under the Queen. That this echoes 2013 Independence White Paper, Scotland’s Future, drafted by one Nicola Sturgeon, is no accident. That was not a prospectus for separation, but for confederalism, as some of us argued at the time.

After all, what does Westminster really need from Scotland? It needs a common travel area, a viable internal market, a common currency, defence and mutual security. That’s really it. England doesn’t need the hassle and expense of the day-to-day running of Scotland; it just needs a recognition that Great Britain still exists as a geopolitical entity and that the UK is a unitary economic space – just like the EU.

This kind of relationship would make sense following Brexit. Scotland would cease to be a Barnett supplicant. The Scottish Government would have to take responsibility for managing economic affairs within the constraints of legally-binding Treaty obligations.

I think Dominic Cummings would be all over this. I think Sir Keir Starmer might be too. A new Union that saves Britain from Balkanisation and emphasises solidarity and common interests would be supported by the Liberal Democrats.

Indeed, it is not inconceivable that Ms Sturgeon might see some merit in an Act of Disunion. It gets her off the referendum hook and would allow her to claim that Scotland was becoming independent, not by conflict and disruption as in Catalonia, but through reasoned discussion and negotiation.

At any rate, something has to be done. Britain finally leaves Europe in the New Year – just in time for the Holyrood elections, which promise to be a blood bath for the unionist parties. Boris Johnson can’t just pretend it’s business as usual. Offering more cash backed by dark threats won’t wash.

Scotland needs to be sorted so he can concentrate on Brexit. If and when the SNP wins a majority in May’s Scottish elections, the Prime Minister should show true Churchillian radicalism by offering his own Plan B – challenging Scotland to join a new partnership of equals. Call it conscious uncoupling. The Union is dead, long live the Union.

Our columns are a platform for writers to express their opinions. They do not necessarily represent the views of The Herald

Read more: Scottish Government's illiberal hate crime bill must be sent to the knackers yard