The Scottish Tories look like supporting more devolution. Cue predictable apoplexy from some. Devolution was a terrible mistake, slopes are slippery, beaches should be fought on and ditches died in.

In its own way, this reaction makes exactly the same mistake as nationalists. To understand why needs a history lesson, and a grasp of public opinion. Let’s start with the history.

The Union of 1707 was a genuine deal. After a military standoff, England knew it couldn’t conquer Scotland. But Scotland was broke, and couldn’t afford to stay independent. The deal put into practice a Scottish scheme for dealing with the problem that was England. A union that preserved in Scotland the things that really mattered; not its mediaeval parliament, but its legal system, which kept the elite happy, and its church, which mattered much more to most people.

It’s easy today to forget how significant the church then was: wars had been fought over the ‘true protestant religion’. You might think that there couldn’t be more than one, but the deal required the Monarch to agree it was one thing in England and another in Scotland. She still does. The Church of Scotland, in which many people had a place, mattered much more to them than the old Scots parliament, in which few had a voice.

Such domestic government as the 18th century had was built around Edinburgh’s legal establishment, from which the great fixer Henry Dundas ran Scotland. He still surveys Edinburgh from a column nearly as high as Nelson’s. But as the British state grew in the 19th and 20th centuries, separate Scottish Boards, Commissions and departments grew too. More responsibilities were added piece by piece, notably by the Thatcher government.

So separate Scottish institutions were built into union from the start.  But by the irreligious late 20th century, a separate church mattered to many fewer; and in a world of universal suffrage, elite rule had to give way to democratic. So some form of elected Scottish Assembly or Parliament was inevitable, and it finally arrived in 1999.

This is reflected in Scottish public opinion. Recent comparative research shows that Scots are more committed to decentralised decisions and their own identity than in other comparable places–Catalonia, Bavaria and so on.

Nationalists draw the wrong conclusion from this, but the majority of Scots don’t confuse their powerful national identity with a separate state. Nationalism may appeal to the heart, rather than the head. But it’s precisely half-hearted. The soul might indeed be dead which did not warm to the story of Scottish identity and culture: but it would be barren too if not moved by shared British history and achievement.

The truth is, this commitment to Scottishness reflects just how much of it there has always been. Of course it was heightened by the divisive economic history of the 1980s, and emphasised by a Scottish Parliament, but unionists should not fall into the same trap as nationalists – seeing it as a trend towards separation – and fighting it tooth and nail.

Where Britain has failed so far, though, is in adjusting the union to reflect the fact that Scottish distinctiveness now has an elected edge. Westminster created a Scottish Parliament – and Assemblies in Cardiff and Belfast – but itself sailed on as if nothing had happened.

Where the legislature been obtuse, locked into inactivity by a half-understood notion of parliamentary sovereignty, the judges have been subtle. With very little material to work on, the Supreme Court has developed a sophisticated devolution jurisprudence. The judges realise the UK now has multiple legislatures, each with real democratic legitimacy.

What the country needs, of course, is a properly defined territorial constitution. Perversely, delivering it will probably be an SNP achievement. If Scotland chooses to stay British – as the polls suggest – separation will be off the agenda ‘for a generation’. That provides the opportunity to look at territorial questions properly, not through the lens of appeasing nationalist sentiment, and develop a proper UK framework that deals with Wales, Northern Ireland and, most significantly, England too.

There is nothing new under the sun. The issues to be resolved are the same Gladstone struggled with over Irish home rule – taxation and representation. He failed, struggling with the intractability of the problem, and a roadblock of Tory resistance.

The taxation issues are complex, but solutions are beginning to emerge. The Government has already legislated to make the Scottish Parliament fiscally responsible, adjusting the funding system accordingly. The Conservatives, and the other parties, might now want to take this further.

Representation is harder. Westminster is England’s Parliament as well as the UK’s, and the asymmetry of having non-English members might be problematic. But it doesn’t need a written constitution to fix this. Help is at hand from the McKay Commission. Perhaps its creation was driven by English Conservative frustration about Labour governments, but its proposals for dealing with the West Lothian Question are balanced and sensible: just as a constitutional convention has developed that Westminster does not legislate on devolved matters, they suggest a convention that Parliament listens to English voices on English laws, as English opinion seems to want.

Supporters of the union can have a positive, well thought through, proposition. A union true to its historical foundations, and in line with UK public opinion.  They must make that proposition to the whole UK, which is not just a bystander in the Scottish referendum.

So take some pills for the apoplexy: remember it’s an accident of history that ‘Unionist’ in the Tory party’s name refers to past debates about Ireland. That’s not the sort of union being challenged in the Scottish referendum, and unionists must make sure to defend the right one.

‘Scotland’s Choices’ by Iain Mclean, Jim Gallagher and Guy Lodge is published by Edinburgh University Press this month

Tags: Alex Salmond, England, Scotland, Scottish independence, Unionism