Sometimes it’s not what you say, it’s what people hear. For anyone under a certain age, it was thoroughly unremarkable when John Swinney said he ‘would enjoy the cooperation with counterparts in Plaid and Sinn Fein’ in order to ‘change the dynamics of the United Kingdom’.

It’s only to be expected that three parties committed to ending British rule in their respective nations would want to work together.

For those who’ve made a few more trips around the sun, Swinney’s comments summoned up memories of the Troubles and Sinn Fein’s historical role as the political face of Irish republican terror. 

Cooperation is especially offensive given the predilection of some Sinn Fein politicians for commemorating the IRA and whitewashing its bloody crimes.

I am as opposed to Northern Irish secession as I am to the Scottish variety. I also oppose Welsh independence and, since I’m on a roll: Mr Trump, the Falklands are British and will be remaining so.

Nevertheless, Sinn Fein is a democratic political party, as is the SNP. Their overlapping causes (a united Ireland, Scottish statehood) are lawful and successive UK governments, Labour and Tory, have been content to work with them.

Elizabeth II famously shook hands with Martin McGuinness, a convicted terrorist, and Westminster signed a peace agreement on Northern Ireland that led to former bombers and their apologists being rehabilitated as legitimate representatives of their communities.

If the SNP wishes to make common cause with Sinn Fein, that is a matter for those two parties. More troubling is Swinney’s reference to the apparatus of the state. 

Asked to explain his assertion that ‘the United Kingdom would be changed irreversibly’ if the SNP and Plaid Cymru win on May 7, the First Minister cited ‘the fact that all of those three countries would be led, potentially, by governments that are committed to fundamental change in the United Kingdom’. 

This would alter ‘the nature of the discussions that would then be taking place around the United Kingdom and between the devolved governments and the United Kingdom Government’.

This describes something very different from cooperation between political parties. What Swinney seems to hint at is the prospect of devolved administrations working together to bring about the demise of the UK as currently constituted. That is, parts of the British state colluding in a campaign against the state itself.

That ought to cross a line. Devolution was not set up for this purpose. Devolved administrations have extensive duties which do not include trespassing into constitutional matters.

Unionists are great ones for rules and are baffled and appalled when their opponents disregard them. But politics isn’t about rules, it’s about power, and if you don’t want your foes to use power against you, don’t give them power in the first place.

Democracy is not a prisoner of the Scotland Act. When Labour set up the Scottish Parliament in the wake of the 1997 referendum, it effectively said that the Scots must govern themselves in a wide range of areas.

When the Tories amended the Act — twice — to transfer further powers to Holyrood, and without any referendum this time, they inadvertently confirmed Ron Davies’ assessment that devolution was ‘a process, not an event’. Not only the powers of the parliament but the scope of the voters to grant mandates was expanding.

Devolution said Scotland should govern itself on almost every issue but in four elections in a row — and likely five come May — Scotland has elected a party whose explicit and primary purpose is to see Scotland govern itself on every issue.

The logic of devolution is the logic of independence not carried to its natural conclusion. It is the idea that Scotland must govern itself, just not too much. Yet having set up a proto-state apparatus, including a Scottish parliament and a government with an army of civil servants and a treasure chest from which to buy the loyalty of the voluntary sector, devolutionists are ignored when they demand separatists not use this apparatus to advance separation.

The problem is devolution itself. Imagine the year was not 2026 but 1996 and the leader of the SNP announced his eagerness to work with Sinn Fein to break up Britain. It would have struggled to make a nib on the politics pages. 

The SNP was barely a parliamentary rump, with fewer Commons seats than even Plaid Cymru. It was devolution that gave the SNP the opportunity and the platform to become the dominant party of Scottish politics and it was devolution that gave them their first taste of executive power and control of institutions which they have since placed in service of their constitutional objectives.

Devolution was a historic error for Britain, an extraordinary act of national self-harm that will continue to imperil the Union, especially though not exclusively, when separatists dominate the Scottish Parliament.

It might seem tempting to throw up your hands and wail in despair but a more practical course of action would be to do something about it. Despite the constitutional damage it has inflicted, there is no prospect of the devolution error being undone any time soon.

As Chesterton put it: ‘The business of progressives is to go on making mistakes. The business of conservatives is to prevent mistakes from being corrected. Even when the revolutionist might himself repent of his revolution, the traditionalist is already defending it as part of his tradition.’

So the answer must be reform. Among the many flaws of the Scotland Act is the latitude it grants to the devolved parliament and government. 

The issuing of the Section 35 order against the Gender Recognition Reform Bill was a dramatic moment because Holyrood so rarely faces consequences for straying into reserved matters. Time to create some more consequences.

The Scotland Act should be amended to create a legal duty for the Holyrood and Westminster governments to preserve the national unity and indivisibility of the UK and for each to respect the constitutional status, institutions, powers and functions of the other. 

The language here is drawn from Section 41 of the South African constitution, a document highly regarded among political and legal theorists.

Unionists behave as though their opponents ought to play by some unwritten rules of good sportsmanship but the only rules that matter are laws. 

Make it unlawful for either government to work towards breaking up the Union, except in the scenario of a future referendum, and you shut down an avenue that has consistently distracted the political class for almost two decades now.

Obviously, the SNP would still be free to campaign for independence as a political party, but when its ministers exercise the functions of the Scottish Government, the law would require them to set aside their constitutional agenda. Agitate to break up Britain in your own time and on your own dime.

Devolution reform is the only hope for steering this system back to its original purpose and nudging the Scottish Government into serving the public within its areas of responsibility rather than exploiting the system to wage constitutional war on the UK.

As for John Swinney, he might want to reflect on who he makes friends with and how he talks about them. This may be just another election message to him but to some people in this country the name of Sinn Fein stirs up fraught, frightening, painful memories. 

The First Minister ought to exercise caution, to say nothing of good taste, when discussing such matters.