Rarely have the ties that bind the United Kingdom seemed so at risk of coming undone. Elections to the Scottish parliament on Thursday seem likely to return a majority in favour of independence, putting a possible second referendum on the issue on to the political agenda. In Northern Ireland, even as it has celebrated the centenary of its foundation in recent days, the ousting of Arlene Foster as first minister and leader of the Democratic Unionist party has upset unionist politics and the political scene more broadly — with potential implications for the UK union.

As in Scotland, Brexit has destabilised the unionist cause; in Northern Ireland, too, a majority of voters backed remain. But an additional source of friction is the protocol linked to prime minister Boris Johnson’s EU withdrawal agreement. Unionists dislike the way that deal treated Northern Ireland differently from Great Britain; it was already a factor in the worst riots in years last month.

To avoid a hard border with the Irish Republic, the protocol left the region within the EU’s economic orbit and subject to its customs rules. That created an economic “border” with the rest of the UK, in the Irish Sea. Johnson’s blithe promises that such a border would never come to pass, and customs and regulatory checks would be invisible, have proved empty.

More lies behind Foster’s departure than just unhappiness about the protocol. The DUP has disastrously mishandled the entire Brexit process, losing votes in its own community as a result. Foster’s downfall is a result not just of her miscalculations — such as trusting the prime minister over Brexit — but her status as a relative moderate in her party. It also reflects the party’s declining stand in the polls.

It remains unclear who might emerge as Foster’s successor but a more hardline stance seems likely to emerge. Edwin Poots, the creationist agriculture minister, appears the frontrunner — but has said he does not want to be first minister (the DUP may separate the roles of first minister and party leader). The other declared contender, the Westminster MP Sir Jeffrey Donaldson, may prove more pragmatic. Either way, squeezed by the breakaway Traditional Unionist Voice, the DUP is likely to become more obstructionist on the protocol and more conservative on social issues. Poots has said he is already seeking advice on a judicial review of the protocol.

A more fractional and broken unionism could allow Sinn Féin to emerge as the largest party in the next Stormont election, with destabilising consequences. It remains in all parties’ interests, however, to have a functional executive in place.

The Johnson government has a key role to play in helping to ease the tensions in Northern Ireland. That means negotiating constructively and in good faith with the EU an agreement on how to implement the protocol. The best outcome may be a light-touch border regime where the UK sticks informally to EU food safety rules to minimise disruption. That would address some of the harm inflicted by Johnson’s last-minute Brexit deal and his pretence that there would not be any non-tariff barriers.

But the DUP should also seek a more constructive path. Its cause has often seen hardline leaders turn pragmatic once they secured their position. This would be in its own interests again. Escalating tension is self-defeating. The best hope for unionists lies not in constant division and violence but in its absence; in persuading those not strongly committed on either side of the Irish reunification debate that the status quo is best left undisturbed.

Letter in response to this article:

Minority rights are key to any solution in Ireland / From John Ure, Singapore