‘The UK is due to leave the European Union’ says a bilingual advisory brochure that has been available in public buildings across the Republic of Ireland for some time. The document offers advice to business on ‘Getting Brexit Ready’: ‘Review your supply chain’, ‘Understand the new rules for importing from or exporting to the UK’. When first published, at a time when there was a certain lack of urgency about the prospect of Britain leaving the EU, it delivered an early warning.

Brexit is a more pressing issue now. The term in vogue these days is a ‘bad Brexit’: as things stand on October 31 – at 11.00 am to be precise – Britain will leave the EU. If it leaves without a deal, what would be the consequences for the Irish economy?

After many reports – they come out almost daily these days – it’s possible to answer that question with a degree of accuracy. The extent of the damage that could result from a ‘bad Brexit’ is becoming clear. In the Republic of Ireland, as many as 80,000 people may lose their jobs, and growth will slow, or even stall, in the years to come. The government has warned that it may have to run a fiscal deficit. If your company does business with Britain, or if you work in an exposed sector, such as food and drink, you should be concerned.

And yet to know what is ahead brings a sense of relief. Brexit will be a nuisance, but it probably won’t drive the economy back into a recession. It has even been something of a boon to Ireland in that it has engendered a sense of national solidarity and purpose: the opposition parties back the government’s stance on Brexit, as do most citizens. The Irish position is uncompromising: senior politicians, such as Taoiseach (prime minister) Leo Varadkar and foreign minister Simon Coveney have repeatedly told Britain that they will oppose the re-introduction of checkpoints and controls on the border between the Republic of Ireland and Northern Ireland, a constituent part of the United Kingdom, in the event of a disorderly Brexit.

Why this insistence? The reasons are both economic and political. The Irish border has been ‘frictionless’ for more than two decades, and almost everyone on the island wants it to remain so. A disorderly Brexit would imply the end of regulatory alignment between the two parts of Ireland and could reverse the integration of the two economies; it could ‘devastate’ the smaller, and much weaker Northern economy, says Simon Coveney, a man not given to hyperbole. The dairy industry is a good example of the coming disruption. Milk produced and sold in the North is often pasteurised on the other side of the border. What happens if Britain adopts its own regulations governing the sale and supply of milk? Would milk still travel as easily? If inspections prove necessary, who would carry them out, and where? Would regulatory divergence require the construction of expensive new processing facilities in Northern Ireland?

The questions and the uncertainty irk the Brexiters who have failed to anticipate them. They have been slow to understand that taking the UK out of the EU and the Customs Union would create separate economic areas and necessitate inspections of goods passing between them: border controls, in other words. These the EU is refusing to accept, at Ireland’s insistence. Brexiters are split on the idea of leaving Northern Ireland in the Customs Union: it appeals to some of them, but not to the hard-liners who argue that it would loosen the union between Great Britain and Northern Ireland.

The EU’s backing for the Irish government, and its toughness with Britain, have, incidentally, helped restore Irish faith in Europe, a faith somewhat strained by the EU’s insistence in 2011 that Ireland seek an international bailout to help it deal with its distressed banks.

By now, at this late stage, we have a fair idea of the economic consequences of Brexit for both parts of Ireland; its political consequences are less knowable and therefore more worrying. What people in Ireland fear most is that Brexit will destabilise Northern Ireland and perhaps lead to another round of conflict there. Northern Ireland is vulnerable to shocks. It is a rickety entity without a functioning government; it is divided against itself, with a large nationalist minority favouring union with the Republic, and a slight unionist majority favouring continued British sovereignty. Political violence has afflicted it throughout its history, particularly during the 1970s and 1980s. The place is largely at peace now, as a result of the Good Friday Agreement of 1998. The GFA, arguably the founding document of modern Ireland, has worked because it offered something to everyone: it assured unionists that they would remain part of the UK for as long as they wanted; it earned nationalist support by facilitating the integration of the two economies on the island, the dismantling of border installations and demilitarisation. The GFA didn’t deliver a united Ireland, but in some minds, at least it has smoothed the way towards it.

A disorderly Brexit could undermine what was effectively a peace treaty. Those who warn that it will cost more than jobs in Northern Ireland employ a baleful logic. It will involve the inspection of goods passing between the two areas, which in turn will necessitate the erection of border installations. At the EU’s behest, a reluctant Irish government may have to build these on its side of the border; Britain, similarly, will feel a need to control its new frontier with the EU. Brexiters often talk of ‘technology’ and how it might obviate the need for border checks and controls, but when pressed for specifics about this ‘technology’ – how it works, who makes it – they offer little in the way of enlightenment.

Border installations, which many will regard as symbols of the enduring and unwanted partition of Ireland, will likely become the focus of angry protests. They would be obvious targets for republican paramilitaries, and as such would require protection: a PSNI (Police Service of Northern Ireland) source confirmed this to RTÉ, the Irish public broadcaster:

“Surveillance, cameras……You’re likely to respond by making buildings more safe and protected, maybe armoured glass fences, fortifications. You’re also likely to respond by the use of police officers. And when you put police officers down into a border situation, inevitably they will be carrying guns. They will be using armoured vehicles and they will themselves present a target opportunity for murder, or attempted murder by dissidents.”

‘Dissidents’ is the blanket term for republicans who reject the GFA and the continued existence of Northern Ireland. Some of them espouse violence. If the PSNI could not, would not defend the installations against their attacks, then the British army would have to. The renewed presence of British soldiers would further infuriate nationalists.

Brexit may or may not create the conditions for a return to violence, or for re-militarisation of the Irish border, but its imminence is already reshaping people’s political thinking in Northern Ireland. Liberal, pro-EU unionists have begun to consider their constitutional future. Northern Ireland voted by a small majority for the EU, nationalist areas voting overwhelmingly to remain, unionist areas voting narrowly to leave. Polls and surveys since then have indicated that a growing number of unionists regret voting to leave the EU, and are now anxious to keep Northern Ireland in the union, or at least as close to it as possible. An obvious means of doing so is to move closer to the Republic of Ireland. Unionists are now giving serious consideration to something they once rejected out of hand, wondering if a united Ireland is a price worth paying in order to stay within the EU. The popular actor Jimmy Nesbitt speaks for many.

Born and raised in the strongly unionist town of Broughshane in County Antrim, he recently came out in favour of a ‘new union of Ireland’, as he revealed plans for an initiative to stimulate discussion on the future of Northern Ireland. We rarely hear from representatives of Northern Ireland’s large immigrant population, which is largely made up of citizens of Eastern European EU member states, but it must be safe to assume that they too would accept Irish unity in return for remaining within the EU. Most British people would passively support the reunification of Ireland. Some take an interest in Northern Ireland, but most do not feel the same emotional attachment to the union with Northern Ireland, as they do to the union of England, Scotland and Wales.

In Northern Ireland, a large but dwindling minority still hews to the cause of leaving the EU. Its largest party, the DUP (Democratic Unionist Party), supports Boris Johnson, but it is much more animated by concern for the maintenance of the United Kingdom than hostility to the European project. In the Republic of Ireland, advocates of leaving the EU, or of breaking from its ranks to deal independently with the UK, inhabit the political fringes. Boris is taking the island to a place where most of its people do not want to be.

Europeans have learned a great deal about Ireland over the last three years, as Britain and the EU continue their interminable attempts to recast their relationship. Another country they may hear much about in the future is Scotland. It produced a solid pro-EU majority three years ago, and its citizens will resent being forced to leave the European Union, something they will regard, and with some justification, as an affront to democracy. If Brexit works out badly, and there is every reason to expect that it will, the next referendum on independence may well produce a majority in favour of calling time on the UK and negotiating Scotland’s return to the EU.