Police officer John Caldwell was shot in Northern Ireland. Why is this so significant?

The DUP boycott of the Northern Ireland Executive, abetted by their supporters in the Conservative Party, is entirely unnecessary, ineffective and inappropriate – not to mention dangerous

We can’t know for sure who was responsible for the shooting of an off-duty police officer at football practice in Omagh, but we do know that Detective Chief Inspector John Caldwell had been investigating drugs gangs and dissident paramilitaries (the two are sometimes connected in Northern Ireland).

We also know that the Police Service of Northern Ireland (PSNI) says that the dissident republican group, the New IRA, is the "primary focus" of their investigation.

Distressing at any time, the attempted murder – DCI Caldwell is “critical but stable” in hospital – is a reminder that the endless dry, circular arguments about the Northern Ireland Protocol and the Belfast Good Friday Agreement have consequences far beyond the possibility of EU Single Market rules being referred to the European Court of Justice, or how many checks should be made on a Tesco lorry at the Port of Larne. It's a matter of life and death; and some have taken peace in Ireland for granted for too long.

Those DUP politicians and their posturing Tory allies who now hold the power-sharing executive in Northern Ireland hostage to their impossibilist demands should know better. Many grew up during the Troubles, with some losing loved ones; yet they play with fire.

The Good Friday Agreement, coming up to its quarter-century anniversary, wasn’t the usual sort of political coalition agreement, even in Northern Ireland. It was in effect a peace treaty; a settlement of a civil war that had itself dragged on for the decades, taken thousands of lives and destroyed families.

In fact, it was the second instalment in a peace process that began with the Downing Street Declaration in 1993, and was only partly completed – after a long boycott by the DUP – with the St Andrews Agreement in 2007, which devolved criminal justice to Belfast.

Since then, as we see again now, it has catered and been subject to withdrawal by Republicans too. It is, even in good times, fragile. Brexit, and the botched deal negotiated by Boris Johnson, betraying his DUP allies into the bargain, has placed peace in even greater jeopardy.

Given the underlying bitter conflict dates back 800 years, the peace process may never be be "complete". All the more reason not to take risks with it.

It’s sometimes argued by the DUP that the NIP runs against the principle of consent in the GFA. It does, because it’s an international treaty and it’s up to the UK parliament to make the rules. It can’t be vetoed by one party, or community, in one devolved parliament.

Tell the Scots about that; ripped out of the EU against their will, straining that part of the Union. Also, tell that to the wise majority of the people of Northern Ireland who could see what might be coming, followed the advice of John Major and Tony Blair – two men who did as much as anyone for peace – and voted to remain in the EU in 2016. It's worth saying: despite their profile and their pompous ubiquity, the DUP does not speak for the people of Northern Ireland.

Given that the NIP can never be reformed in a way that will satisfy the DUP (or so it appears), their boycott of the power-sharing executive will presumably also be permanent, in which case power-sharing, the GFA and peace will also slowly fall.

But let's think. What if the UK and EU miraculously ditch the NIP and move the economic and trade border to the poltical land border between Northern Ireland and Ireland, and challenge the EU to put in border checks and customs posts? The DUP would then be happy, they claim, to rejoin the NI Executive; but then Sinn Fein, at least, will withdraw from it and, probably denounce the GFA.

Jeffrey Donaldson and his friends will walk through the front door of Stormont – but Michelle O’Neill and the others will be exiting from the back door. The threat of Loyalist violence, which has been building, subsides with the NIP gone and a hard border in place, but the Republican men of violence will rise up once again.

The DUP boycott of the Northern Ireland Executive, abetted by their supporters in the Conservative Party, is entirely unnecessary, ineffective and inappropriate – not to mention dangerous. The struggle to change the NIP can better take place through the NI Executive with the Assembly in place.

The brutal truth is that the governance of the UK and its relations with the EU can’t be made subject to the veto of one minority party in one community in the UK. The older, smaller Ulster Unionists see this, and want to return to government even as they oppose the NIP.

It’s (maybe) true that Rishi Sunak wouldn’t be working so hard to get concessions now without DUP pressure, but whatever its uses, the DUP's blackmail tactic has run its course. Whatever Sunak comes back with is as good as it gets.

The DUP have a choice. They can compromise and live with what they will get, rejoin the NI Executive, and make do with Donaldson as deputy first minister and O’Neill as first minister. There’s nothing to stop them trying to get the way the NIP changed again as time goes on.

Or they can persevere with the boycott. That will have two unfortunate consequences. It will steadily push Northern Ireland back to the bomb and the bullet. Not, perhaps, the full-blown civil war and breakdown of the rule of law in the early 1970s, but to use the awful old euphemism, “an acceptable level of violence”. That will also help push Northern Ireland out of the UK.

Such a prospect will force many, including in Great Britain, to think the unthinkable, and reconsider a united Ireland within a European Union, which would dissolve the border and all it entails for ever. The law of unintended consequences can be cruel to those who push things too far.