The DUP was split over Brexit, according to Jim Wells.

“There were those who were extremely happy to leave and those who were ecstatically happy to leave”, says Wells, a DUP member of the collapsed assembly at Stormont.

Wells claims the decision for the party to back leaving the European Union took “all of five minutes” in 2016. Asking if the DUP was pro-Brexit was “like asking if we were royalist — it’s just the way we are”.

But two years on from the referendum vote several DUP figures admit that the process of leaving the EU is more complex than they had reckoned, particularly in Northern Ireland, where the vote has rekindled serious discussion of a united Ireland. The European Commission has made it explicit that Northern Ireland would retain EU membership if it were to secede from the UK and join the Republic.

Ian Paisley Jr and Sammy Wilson with Arron Banks and Andy Wigmore after a select committee appearance on their Russian links (Source: Twitter)

Even the normally-strident Wells pauses for thought when asked if he believes the Brexit vote has strengthened the union. “That’s a difficult question”, he says after a rare pause, admitting that many of those nationalists who were fairly content with the status quo are now feeling uneasy.

“There was an acquiescence among some nationalists that if the EU was here they were content as long as things were going well economically. But I’m very confident that when there isn’t the Armageddon that’s been predicted people will be settled.”

Gregory Campbell, the DUP MP for East Londonderry, concedes the negotiation is “more slow and more complicated than we thought”.

He said: “I, like most people, knew it wouldn’t be straightforward but I didn’t think anyone suspected it would be as long drawn-out, complicated and divisive [a process] as some people are trying to turn it into.”

Campbell, like Wells, believes that Brexit may in fact bolster the union in the long run by bringing economic benefits. More immediately he accepts that it has invigorated talk of a united Ireland among those who “wouldn’t want to be described as unionists” but were previously happy for Northern Ireland to remain part of the UK.

Sinn Fein’s “Irish identity project”, Campbell says, amounts to a zero-sum debate where Irishness is perceived as incompatible with Northern Ireland remaining part of the UK and that this argument will fall flat once Britain has made a success of Brexit. “In five or ten years’ time, the negotiations, Brexit, the transition period will have been completed and I think you will see a move away from this zero-sum game because they can’t win that. But I want to see the next two or three years over and done with.”

He adds: “That group will never be flag-waving, 12th of July unionists but they’ll be quite content with the status quo of being part of the UK with access into the EU across the border and they will see that as being the best of both worlds.”

Two younger DUP members suggest that outside of the Westminster group there was a greater pragmaticism over Europe, particularly among younger members, with one describing Alastair Ross, Simon Hamilton and David McIlveen as “reformers rather than ardent leavers”.

One figure familiar with DUP policy-making said that the party gave little thought to the nationalist response to Brexit, suggesting that the party was lulled into a false sense of security by Sinn Fein’s previous Euroscepticism. More than one DUP source pointed out that Sinn Fein did not campaign for a remain vote and that the turnout in nationalist areas was lacklustre.

The DUP’s enthusiastic embrace of Brexit has drawn them into an intimate alliance with hard Brexiteers who appear more interested in leaving the EU than keeping the UK intact.

The embrace is in some ways an awkward one. Hours after Britain voted to leave the European Union, Arron Banks sent a congratulatory text message to Nigel Farage summing up their achievement.

“In the last day we have won the referendum, fucked Cameron, fucked Corbyn, caused a second referendum in Scotland, caused a discussion of a united Ireland…”, Banks wrote to Farage, who fronted Banks’s Leave.eu campaign.

Banks’s apparent glee at the prospect of breaking up the UK was not on the menu when he appeared alongside Farage at a DUP fundraising event held by Ian Paisley Jr last month in Antrim.

The appearance of the self-entitled “bad boys of Brexit” sparked a flurry of bizarre stories speculating that Farage could seek election to Parliament by joining the unionists.

Yet earlier that month Farage himself asked listeners on his LBC radio show if it was “now time for us to cut adrift Northern Ireland so we can get the kind of [EU] trade deal we want?”. His answer was ultimately ‘no’, but not before he asserted that “over the last half century we’ve had an increasing sense of detachment from Northern Ireland — it has felt less and less part integrally of the United Kingdom”.

Farage’s apparent ambivalence towards Northern Ireland’s place in the UK is echoed by Banks, whose Twitter stream suggests he is more certain of Crimea belonging to Russia than of Northern Ireland being part of the UK.

Banks recounts in his book The Bad Boys of Brexit how he told Chris Montgomery, the DUP’s chief of staff in Westminster, of his plans for campaigning in “the UK and Northern Ireland”. He writes that Montgomery “sent a snotty reply pointing out that Northern Ireland is in the UK and that I should make sure I realise that if I am going to try going over there”. Banks claimed in his book that the DUP demanded “cold, hard cash in exchange for their support”, which he characterised as extortion. The DUP denied the claim.

The inherent tension in the DUP’s courting of the hard Brexiteers came to the fore last month when Jacob Rees-Mogg, chairman of the hardline European Research Group of Conservative MPs, reportedly clashed with the prime minister over her reluctance to put the union at risk by alienating moderate nationalists.

The clash between the prime minister and Rees-Mogg presented an opportunity for Michelle O’Neill, Sinn Fein’s leader in the north of Ireland, to call for a referendum, arguing that the prime minister’s uncertainty over the outcome of a referendum met the threshold for holding a border poll under the Good Friday Agreement.

Recent polling suggests that the levels of support for a united Ireland are far below the threshold for triggering a referendum. But support for the status quo among Catholics (page 45) is highly sensitive to the impact of Northern Ireland leaving the EU.

The DUP contends that Brexit will bolster the union if it delivers economically for Northern Ireland. That remains an ‘if’ of historic magnitude.