CONSIDER the Davidson dilemma. The Scottish Conservative leader, Ruth Davidson, is probably the best political leader the Tory Party has thrown up in 40 years: modern and radical, without abandoning Tory virtues of self-reliance, aspiration and Unionism. But this week as she addresses her party conference, she faces an impossible contradiction: how to reconcile her support for soft Brexit with membership of a party that is going in the opposite direction, and could conceivable have Jacob Rees-Mogg as its UK leader. They’d make the oddest couple in political history

David Mundell, the Scottish Secretary, has tried to paper over the cracks by raising the threat of an early independence referendum, but that is futile. No one expects Nicola Sturgeon to announce a referendum any time soon. Yet today the phoney war over Brexit finally comes to an end as the EU publishes its voluminous draft treaty based on the phase 1 “divorce” agreements struck chaotically before Christmas. Out of that farrago of fudge and contradiction, a team of Brussels lawyers has drafted a closely-argued legal text. It says there will be no extended transition period, as mooted by the UK Government in its recent position paper. Britain will be out by the end of December 2021, and the European Court of Justice will rule on all questions of trade dispute. Mr Rees-Mogg will condemn this as a Brussels diktat that makes Britain a “vassal state”, without the ability to strike its own trade deals or change the laws of the single market.

That is contentious enough, but the Irish border section is much more problematic. Britain agreed in December that there will be “full regulatory alignment” between Northern Ireland and the single market, and the draft treaty takes that literally, echoing Jeremy Corbyn’s claim that the North will have to remain in the EU customs union. Theresa May’s December reference to “no regulatory divergence with the rest of UK” has been dropped on the grounds that relations between Northern Ireland and the rest of Britain is an “internal matter”. And no, the Foreign Secretary Boris Johnson’s ingenious proposal yesterday to treat the Republic of Ireland for border purposes as if it were a local council like Camden or Westminster will not be endorsed by Brussels.

Tory MPs in the European Research Group are adamant that Mrs May must refuse to accept these terms, but it’s not entirely clear what her options are if she does. It would mean accepting that Britain crashes out of the EU early and without any agreed trade deal, short of World Trade Organisation rules. This is the final collision with reality; the last hurrah for the cake-and-eat-it strategy. Brexiters like Mr Johnson had forecast that the EU would cave in eventually and accept that Britain can be both in the single market and out of it. That it can have free trade in goods and services with the EU and yet not recognise the European Court of Justice, and be free to make trade deals with non-EU countries without losing any of the privileges of EU membership. This is what Brussels calls “magical thinking”. The spell has been broken.

But the implications for the UK are profound. Mrs May’s coalition partners in the Democratic Unionist Party have made clear that they will not accept any border emerging, de facto or otherwise, between the North and the rest of the UK. Their red line is that Northern Ireland leaves the EU in exactly the same time scale and under the same conditions as the rest of Britain. They want the North to be as British as Westminster or Camden council. Perhaps Mrs May, in her speech on Friday will find a way to square this circle, but it seems a hopeless case.

Ms Davidson, meanwhile, will have to decide where she stands, not just on Ireland, but on relations between Scotland and the rest of the UK after Brexit, for that is not clear either. David Lidington, the “de facto” deputy prime minister, has said that the powers repatriated from Brussels after Brexit cannot simply land, untouched, in Holyrood. Scotland cannot be allowed to have different standards of food safety and animal welfare from the rest of the UK. Nor can it simply take over the half-billion pound funding stream from the Common Agricultural Policy, most of which comes via the UK anyway.

Just as many UK Conservatives have never really understood the implications of the Good Friday Agreement, nor have they really appreciated the significance of the 1998 Scotland Act. This famously asserted that any matter not specifically reserved to Westminster automatically becomes a responsibility of the Scottish Parliament. This means that, as the House of Lords EU committee agreed in July, that powers repatriated from Brussels on agriculture, environment and so on become powers of Holyrood “by default”.

Many in the UK Government suspect that Nicola Sturgeon’s insistence on this constitutional formula is just Nationalist trouble making. That the SNP is trying to drive a wedge between Scotland and England to further its separatist project. But the inconvenient truth is that it has been the Welsh parliament, which is Labour-led, that has been leading the opposition to what the Welsh First Minster, Carwyn Jones, calls the “Westminster power grab”. This is actually a devolution issue, not an independence one.

We can expect a set of new solutions to this problem to be announced this week by the Conservatives to forestall the Scottish Government’s proposed Continuity Bill ( which anyway has been rejected by the Presiding Officer as beyond Holyrood’s competence). It will probably involve some form of joint committee to give the Scottish and Welsh parliaments equal say on the distribution of powers following Brexit. Not just consultation, but co-determination. Whether this will work as an amendment to the EU Withdrawal Bill remains to be seen.

But what is becoming clear is that the issues of the Irish border and devolution are essentially the same. Brexit has come to grief not just over the economic cost of abandoning the wealthiest free trade area on the planet. It has revealed that the United Kingdom is no longer a unitary entity, and that it is not possible for Britain simply to leave the EU “as one nation”.