With a no-deal departure from the European Union on the horizon, a scenario that is apparently being actively pursued by the new administration in Downing Street, it is important to understand what effect this would have in practice, especially in the sensitive and vulnerable context of Northern Ireland. The region has seen a period of relative stability since 1998, but this stability has come into question with the growing possibility of a disorderly exit on 31 October – against the wishes of the majority of the population in Northern Ireland.

The first – and most obvious – effect to consider is the potential effect on Northern Ireland’s fractured peace process. At the very least, a no-deal exit will add further strain relationships between unionists and nationalists. This exchange between the DUP’s Arlene Foster and Sinn Féin’s Michelle Gildernew captures the level of acrimony between the two parties:

These added tensions may not in themselves imply anything beyond strained relationships among the political parties. But they can trickle down throughout society too. Moreover, with an ongoing political vacuum and evidence of persistent activity by dissident republicans, it is clear that people who have never been committed to the peace process will do all they can to exploit that vacuum. Any instability from a no-deal exit could make their job easier.

Much will ride on what happens at the border after 31 October. As the former Taoiseach, Charles Haughey, put it in 1986, “This border is … an artificial line that runs across and divides in two a country which has always been regarded as one, and which has always regarded itself as one.” One of the greatest fruits of the peace process has been a symbolically important open border since the 90s –greatly facilitated by the two jurisdictions being in the European Union.

Both the UK and the EU have endlessly stated that they are determined to avoid this border hardening again. But with Boris Johnson’s administration making demands that the EU will almost certainly reject, it is getting harder and harder to see how the UK’s exit will be smooth and orderly. The no-deal planning of ‘Operation Yellowhammer’ makes it clear that the UK government – for all its public statements – privately acknowledges that interim measures to avoid border checks will be “unsustainable.”

In other words, no deal means the return of checks at the border. Together with the economic fallout from the lack of transition, which the Department for the Economy estimates could cost 40,000 jobs in Northern Ireland, these checks could prove highly destabilising to the region. The PSNI has repeatedly expressed its concern that they would become targets for terrorist attacks. In the words of the former Chief Constable, George Hamilton, a no-deal exit would “magnify all the demands and difficulties” that already exist in promoting peace and security.

And then there is the possibility of a border poll. A no-deal exit would certainly increase the demands for a referendum on Irish unity to be held sooner rather than later. But such a referendum in itself will be far from straightforward to hold. For one thing, it will be logistically problematic: there has not been an Executive since 2017, and significant preparation will be required. As Leo Varadkar recently noted in Belfast, “We believe that there is a high probability that it would be defeated and it would be divisive, I think, here in Northern Ireland,” adding to calls for a more considered debate in advance – in contrast to the UK’s pre-referendum experience with Brexit.

In the event of a no-deal exit in October, the political backdrop is unlikely to be particularly conducive to calm, measured debate. With direct rule almost inevitable under such circumstances, it will reduce the incentives to restore a devolved power-sharing government at Stormont, marking a further backward step as far as implementing the Good Friday Agreement is concerned.

David Phinnemore and Katy Hayward of Queen’s University Belfast have argued that there has been no or little focus by Brexiteers in their understanding of the importance of ensuring that all sections of the community in Northern Ireland have their thoughts heard as outlined under the 1998 Agreement. In evidence to the Northern Ireland Affairs Committee at Westminster, they point out that even in the Withdrawal Agreement and Political Declaration, there are “Gaps in the envisaged arrangements (that) need to be identified and filled accordingly.”

A no-deal exit will magnify the already significant challenges of leaving the EU in a way that commands any kind of cross-community support. The complex politics of Northern Ireland have helped to see the Withdrawal Agreement unravel, and yet the alternative looks set to make Northern Ireland’s politics even more complex. There is only an ever-decreasing window for helping to prevent the worst effects under this destabilising scenario.