CREATING a border down the Irish Sea would be the best way to solve the backstop conundrum and deliver Brexit, the former head of the UK’s Government Brexit department has said.

Philip Rycroft said it was the “simplest way of cutting the Gordian Knot” and would be very attractive to any new government not reliant on the DUP.

“I think that is the one to watch,” he told an audience in Edinburgh last night. 

Mr Rycroft, the permanent secretary at the Department for Exiting the European Union (DExEU) for two years until March, also warned a no-deal Brexit would be “the most scything possible rupture” and said claims that the UK could simply trade on bare-bone WTO rules instead were “fantasies”. 

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No-deal would also see the Irish border become “highly unstable”.

He said the “Brexit frenzy” was dismissive of implications for the Union, and suggested a federal UK may be needed to give the UK a future, given the already “soured” relations between London and the devolved administrations over Brexit.

He said the country was “in the grip of a political and constitutional crisis the like of which the UK has not experienced for decades or, arguably, in its peculiar dimensions, ever”. 

Mr Rycroft also said Tory-imposed austerity in the wake of the 2008 Crash had been a big factor in the Leave vote, as people had seen services cut and felt far removed from Westminster.

He said the then PM David Cameron had miscalculated when he went for a short campaign in the EU referendum when he should have taken his time to change the public mood. A longer campaign would also have meant more Leave supporters had died, he said.

“For the EU referendum, I think what we needed was time. Not least a wee bit of a generational impact. As older people shuffle off this mortal coil... the demographic begins to shift.”

The European Commission first proposed Northern Ireland joining the Irish Republic inside the EU single market and customs union to avoid a hard border dividing the island.

However Theresa May rejected it out of hand as it would split the UK, with Northern Ireland and Great Britain under different trading regimes.

She said it would “threaten the constitutional integrity of the UK by creating a customs and regulatory border down the Irish Sea, and no UK prime minister could ever agree to it”.

The DUP, whose 10 MPs propped up her government, were also vehemently opposed to the scheme, arguing it would separate Northern Ireland from the rest of the UK and advance Irish unification.

But with the Commons arithmetic now different and an election in sight, Mr Rycroft told a David Hume Institute lecture at Edinburgh University an ‘all-Ireland backstop’ could prevail.

He said: “This is the border down the Irish sea. In many ways the simplest way of cutting the Gordian Knot of this. Impossible for Mrs May because of her dependence on the DUP.”

He said there would initially be no checks on goods moving west to east from Ireland into Britain, but there would be checks moving east to west.

“So Holyhead and Stranraer would become  points of external export for both customs and regulatory checks," he said.

“A lot easier to control point to point rather than a long complicated border [across Ireland]. If I was to put money on this, depending on what happens if there’s a general election, I think that solution becomes very attractive to any government wishing to pursue Brexit.”

He said even Tory MPs, despite the party’s Unionism, would “in the stillness of the night accept that as a solution. And of course the EU accepts it because that is their solution.”

On no-deal, he added: “There will be disruption. This is a system with millions of moving parts.

"The Northern Ireland- Ireland border will be highly unstable. The UK will allow goods to come north without let or hindrance, pretty much. The south will require to put in place an external border of the EU. That is not a stable situation, and will have to be resolved very quickly.

“The more serious thing is the long-term economic dislocation. What we’d do is overnight put friction into our major trading relationship for both goods and services. That makes UK businesses less competitive selling into our major market. The same applies to EU businesses selling into the UK, but don’t forget that for them it’s about 9 per cent of their trade versus 45% for us.”