Dr David Shiels is a Policy Analyst at Open Europe and also works on contemporary political history.

Would a No Deal Brexit lead to Irish unity? The possibility of the break-up of the United Kingdom triggered by a chaotic Brexit was reportedly discussed at Cabinet last week, with one minister telling colleagues that the UK was “sleepwalking into a border poll.”

The reports have upset the DUP, angry that the constitutional question has been brought into the discussion at this stage. Arlene Foster, the DUP leader, said it was a revival of “Project Fear.” After coming on board with the Brady amendment to give the Government more time to renegotiate the Brexit deal, the DUP’s lines on the backstop have hardened in the last few days.

Rightly or wrongly, there is a sense that by talking up the prospects of a No Deal border poll, the Government is feeding into a narrative set by Sinn Fein. From the Government, the message to the DUP seems to be “support our deal or take your chances with a referendum.” For a party which already sees the backstop as something which undermines the integrity of the United Kingdom, the fact that the Government is thinking along these lines is disturbing.

Meanwhile, the interventions by John Major and Tony Blair have also gone down badly with Unionists, the two ex-premiers having recently spoken about the impact of a No Deal Brexit on the peace process. (It should be remembered that the joint intervention by the former Prime Ministers during the 2016 referendum was claimed to have encouraged an increase in Vote Leave support in Northern Ireland).

Of course, some will say that the DUP are getting what they deserve. Brexit was clearly a provocation to Irish Nationalists and the party should not be surprised that talk of Irish unity is now on the agenda in a way that it was not before the referendum. There is a sense that the party has trapped itself into supporting a hard Brexit – though the recent intervention by Sir Jeffrey Donaldson, the DUP Chief Whip, suggests that the Party acknowledges the dangers of a No Deal Brexit and wants to avoid that outcome.

Although the Irish Government has been keen to downplay the possibility of a border poll – no doubt aware of Unionist sensitivities over the backstop – there are plenty of commentators and politicians in Dublin who are contemplating unity in a way they had not done before. Even John Bruton, the very moderate ex-Taoiseach, has pointed out that “By backing Brexit at all costs, including a no-deal Brexit, the Democratic Unionist Party has enhanced the likelihood of a border poll that would end the Union.”

Despite these conversations about Irish unity, there are no convincing signs that a change in Northern Ireland’s constitutional position is imminent. True, a number of opinion polls have shown increased support for Irish unity because of Brexit, with more people supporting a united Ireland in that context. The possibility of a No Deal Brexit shows the most dramatic effect, and one opinion poll by the Belfast-based LucidTalk polling company – cited by Bruton – suggested that in the circumstances of No Deal 55 per cent of people would probably or certainly support Irish unity.

It is always difficult to poll for hypothetical situations, however. There is a debate about whether demographics in Northern Ireland favour Irish unity in the longer term – but this would be happening irrespective of Brexit. The most recent actual test of opinion in Northern Ireland – the 2017 General Election – showed that that voters continued to follow traditional patterns of behaviour. The DUP’s vote went up by just over ten per cent on the previous Westminster election, while Sinn Fein’s vote also went up by just under five per cent.

Under the terms of the Belfast Agreement, the Secretary of State for Northern Ireland must call a border poll “if at any time it appears likely to him [or her] that a majority of those voting would express a wish that Northern Ireland should cease to be part of the United Kingdom and form part of a united Ireland.” Some may contend that these circumstances have been met, since the Unionist parties are now polling under 50 per cent at Westminster and Assembly elections.

It could equally be argued that the Nationalist parties would have to win a clear mandate for a border poll before one is called. Much may depend on the position taken by the non-aligned Alliance Party, and whether its anti-Brexit position would lead it to endorse a border poll in the circumstances of No Deal (though there is no suggestion that it would do so). There is also a view, taken by Lord Bew, that the Government could actively use a border poll to determine support for the Union.

Clearly, Unionists must proceed with caution, and they should be prepared for all possibilities. As I have argued before, the fact that all the border constituencies have returned abstentionist Sinn Fein MPs is a sign of considerable dissatisfaction with the existing governance arrangements in Northern Ireland, and this has been exacerbated by Brexit. It is right that the Government takes seriously the concerns of Nationalist opinion.

It may also be that if a Brexit deal is secured, the constitutional question will be taken off the table again.  For as long as No Deal remains a possibility, it is unhelpful for Ministers to speculate about a border poll – particularly as there seems to be little strategic thinking behind this approach. Raising the question is not only counterproductive in terms of bringing the DUP onside, but also adds another element of uncertainty to the current debate in Northern Ireland.