AMID the pullulating Brexit-ScotRef hullabaloo, I’ve been impressed by the still small voice of Guto Bebb, MP for Aberconwy and junior minister at the Welsh Office. He may have a crazy name but he obviously has a sensitive soul, too, as befits a man representing at Westminster the beautiful mountains of Snowdonia.

I must admit I had never heard of Guto before last weekend, but on doing a bit of research I find he has an intriguing background as well. He was born and brought up with Welsh as his first language in a family of staunch nationalists.

He might have made a career in Plaid Cymru, except he could not abide their support for the EU. So he joined the Tories instead, and at length got elected to Westminster. Even so, he was against Brexit.

He is evidently not a mere political opportunist, then, though perhaps a bit too open-minded for his own good.

But what most interests me about Guto is how he has reacted to a recent visit to Scotland, of which he evidently knew little before, as a member of a devolutionary ministerial committee. In a column he writes for his constituents he reports back of the Scots: “Read their papers, listen to talk shows and watch the news and it’s clearly another country.”

Edinburgh now puts him in mind of Dublin, as a capital which, though outwardly familiar, is inwardly foreign: “That is fine in the context of the capital of an independent country but it should be a warning when visiting a city which is a crucial part of the UK ... the sense of nationhood in Edinburgh is palpable. For a long time it has been satisfied within the UK. Is that changing, though? My gut feeling is yes and that should be a cause for regret to all of us.”

Guto will not have done his career any good by saying what he said. Robert Peston, during his chat show, wrung a vicarious apology from the Secretary of State for Wales, Alun Cairns, who is not such a nice man: he once had to resign as his party’s education spokesman in the Welsh Assembly for calling his Italian constituents “greasy wops”. Guto may suffer for a more honourable reason – that what he said is true.

To take the most obvious political point, both Scotland and England were once upon a time components of a common system centred at Westminster, with the same parties and the same controversies. By and large, both nations reacted to the course of events in the same way, swinging now to the left, now to the right. So it was no problem for each to continue occupying its place in the single structure.

Today, inside that continuing single structure, we have two different political systems. The parties and the controversies are no longer the same in the one as in the other. At Holyrood, we are ruled by a party that can never take power at Westminster. At Westminster, we are ruled by a party that has only just come off the life-support machine at Holyrood. It has done quite well, but not so well that it can reforge a single structure or have much prospect of doing so. In this case, I would say, the easiest thing in the long run is that each system should go its own road and pursue its own interests or aspirations. To rephrase the matter, in a single polity of two systems, the two nations concerned would do better to separate.

But how long is the long run? If Nicola Sturgeon gets her way it will be rather short. Despite the rubbishing she has been subjected to across the spectrum of the UK parties, her timetable is in fact perfectly feasible and quite sensible given the aims she has in view. Michel Barnier, the Frenchman who will be leading the Brexit negotiations from the EU side, has himself said that, once Article 50 is triggered in a few days’ time, he wants to get the substantive business finished by the autumn of 2018, so that the second year of the prescribed period for British withdrawal can be taken up with ratification of the deal by the parliaments of the member states. In other words, the shape of the deal will already be obvious halfway towards the two-year limit: time enough for ScotRef to be called and carried through.

Of course, the timetable can slip, and probably will. But if the negotiations become too protracted, it may signal that they are going to fail and that Britain will leave the EU without a formal deal. Some fanatical Brexiteers even favour this, yet Theresa May could hardly count it as a victory and would probably not survive as Prime Minister. In any event, the case for ScotRef surely then becomes unanswerable.

The only caveat to be entered concerns May’s true motivation beneath her statement in response to the First Minister’s call for a referendum last week: “Now is not the time.” May perhaps implies there that the right time might come, yet she does not actually commit the UK Government to anything.

Nor does she, to plumb deeper still, in any way modify the ideology of the British state that rests on the absolute sovereignty of the Crown-in-Parliament. In principle, under such a system, a referendum can be refused simply because the Government does not want one, and under the UK constitution there can be no redress, not even in the Supreme Court.

By contrast, to bring out another aspect of my two-systems theory, the Scottish Government’s position rests on a simple and anti-absolutist assertion of democracy: if Scotland wants a referendum, then Scotland should get one. It is a plain matter of self-determination, a principle the UK first accepted in the Treaty of Versailles in 1919 and upheld all through the dissolution of the British Empire and again during that fresh springtime of European nations after the collapse of Communism in 1989. No reason to make Scotland an exception, then.

It would be better if the UK already had mechanisms in place allowing a petition from a given proportion of the electorate to trigger a referendum on any particular subject, a rule that exists in Switzerland and California. While such mechanisms might be set up in an independent Scotland, in their absence we must make do with the best democratic vote available to us, which will take place in our Parliament tomorrow.

Tory leader Ruth Davidson seems to believe it should all be determined by the state of the opinion polls, but this is unlikely to pass muster as a constitutional principle.

Altogether, Scotland and England not only have developed two different political systems but within it also act on two different constitutional principles: absolute sovereignty and parliamentary democracy. When the Prime Minister goes on about “our precious United Kingdom”, she ignores how deep the divisions have already gone – and have done so almost instinctively, without fundamental debate, probably just because it suits the experience, temperament and interests of the two nations most closely involved in the process. In my opinion it will continue whether we have a second referendum next year, the year after, in 10 years or in 50 years. In the end there can be only one result.