BREXIT poses a fundamental dilemma for independence supporters, say academics.

The most benign form, from the SNP perspective, would be of the soft variety, in which the whole of the UK stayed inside the EU single market.

Both sides of Hadrian’s wall would be in harmony, at least in terms of trade with the EU.

READ MORE: Beyond Brexit: More than two out of five Scots ready to stick with EU even if this means hard border

Not only would this offer a springboard to independence - regulations and laws would keep step with the EU and simplify Scotland’s future re-entry as an independent state - it would also allow the SNP to pace itself.

The independence question could be safely parked for a few years, which was the SNP plan after 2014, until the party felt confident of winning second time around.

The problem is that soft Brexit robs the independence case of a sense of urgency. It makes the mechanics of independence simpler, but it makes the politics tougher. Why take a punt to join the EU when soft Brexit is the best of both worlds, the Unionist argument would go.

READ MORE: Beyond Brexit: More than two out of five Scots ready to stick with EU even if this means hard border

In contrast, a hard Brexit, in which the UK broke with the single market in goods, capital, services and labour, and fell back on WTO rules and trade tariffs, would fuel grievance galore.

Scotland would be dragged out the EU despite its manifest wish to stay.

But while this could provide political energy, it would make the practical side of independence far harder.

If Scotland was an independent EU state inside the single market, and the rest of the UK was outside, there would be a hard trade border between England and Scotland, fracturing the single market within the UK.

READ MORE: Beyond Brexit: More than two out of five Scots ready to stick with EU even if this means hard border

It might not be a physical border with checkpoints - Norway and Sweden use electronic number plate recognition to track vehicles across their border - but it would mean different trading and immigration regimes, and complicated extra burdens on business. It would also put pressure on Nicola Sturgeon to move swiftly to a second referendum.

“The softer the Brexit the better for the independence case,” said Nicola McEwen, professor of territorial politics at Edinburgh University.

“Because then you don’t have the border issues. A hard Brexit, although politically it appears stronger [in terms of advancing a Yes], in practice throws up a lot of difficulties.”

Professor Michael Keating, director of the Centre on Constitutional Change, said Brexit may well impose a choice on Scots - to stay with the UK or go with the EU.

READ MORE: Beyond Brexit: More than two out of five Scots ready to stick with EU even if this means hard border

The SNP’s gradualist middle way - slowly accumulating powers at Holyrood - is vanishing.

He said: “It looks like a hard Brexit. So this middle ground seems to be disappearing very quickly. That’s really worrying, because it’s where Scotland had been going before the referendum, trying to find some compromise between independence and not being independent, because the country is divided right down the middle.”

It all means the likelihood of a second independence referendum has risen sharply with Brexit.

Prof Keating added: “You couldn’t stay in both economic unions, which is the SNP want to do, and most people in Scotland want to do. So people might be forced to choose between the two.

“This is not the doing of the Scottish Government or anybody in Scotland. It’s because of what the UK government has done. They’ve put us in this position.

“I think the SNP could get a bounce if Brexit looked very problematic and started to unravel.

“They could win a referendum, not on the back of Europe necessarily, but because they could point out the UK government had not listened to us.

“But what if Europe goes into meltdown next year? French and German elections, the Italian referendum coming up. There’s a whole lot of booby traps. The SNP strategy would be to say, ‘Europe is a safe haven, post-Brexit Britain is a very dangerous place.’

“But if Europe’s no longer looking like a safe haven that becomes more difficult.”

Prof McEwen said a hard Brexit would also require a new independence prospectus.

“In 2014, the White Paper set out a vision of independence which didn’t just include a currency union, but an energy union, joint ventures for broadcasting, all kinds of cooperation institutionally, politically and economically. It would be difficult to envisage that with Scotland in the EU and the rest of the UK outside the EU, particularly with a hard Brexit.”

The experts agreed Scotland had little to no chance of striking a separate deal with the EU or European Economic Area (EEA) while part of the UK, a “sub-state” in the jargon, as neither the EU or EEA recognise sub-states, only states.

The SNP Government’s plan for such a deal was therefore seen as implying independence. The apparent indifference of the UK government was helping this goal, said some.

Dr Jo Murkens of the London School of Economics said the fundamental tension in the Brexit vote - Scotland voting one way, England another - made a constitutional crisis inevitable.

However rather than forcing Scotland to choose between the UK and EU, it could force the UK government to choose between Brexit and the Union.

“People say if we don’t give effect to Brexit, then the people of Sunderland [61-39 for Leave] will riot and create a political crisis. I say if we do give effect to Brexit the people in Sutherland, Scotland and Northern Ireland will be equally up in arms about Westminster ruling the regions.

“David Cameron and Theresa May have been tone deaf to devolution. They haven’t appreciated devolution has changed constitutional politics in the United Kingdom.

“If Brexit is the ultimate goal, you have to accept Scotland may go its own way, and Northern Ireland might reunite with Ireland.

“But if the overriding goal is to govern in the national interest, then they should do more than paper over the cracks. The United Kingdom is fragile. But right now I don’t see the UK government saying the priority is for the United Kingdom is to survive this.”