As delegates arrive for the DUP conference in Belfast, they might ruefully reflect on what a year it has been.

One year ago EU Task Force officials were locked in fraught negotiations with London over how to deal with the Northern Ireland border question.

Irish Government officials were also closely involved. All sides were hurtling towards a 4 December deadline to sort out the border issue, otherwise the Brexit negotiations would not be moving to Phase II.

British Prime Minister Theresa May was under pressure to deliver.

London had wanted to deal with the border through the future relationship, but the European Union’s Chief Brexit negotiator Michel Barnier’s mandate required it to be dealt with in the Withdrawal Agreement.

The talks were difficult. Dublin was not moving on the need for a backstop solution that was legally operable in the divorce treaty.

Over the course of those weeks an outline appeared: if neither the future relationship nor technology were ready on time, or did the job of avoiding a hard border, then Northern Ireland would remain in the customs union and significant parts of the single market.

The DUP was only given fleeting sight of where things were heading. They had been adamantly opposed to any talk of Northern Ireland somehow staying behind while the rest of the UK left.

When RTÉ News broke the story on the morning of 4 December that the UK had accepted the principle of the North remaining aligned to the rules of the single market and customs union, a DUP delegation was at that very moment being briefed in Downing Street by the Chief Whip Julian Smith.

It was a bridge too far for a party already highly strung over the direction of the negotiations.

Word was sent back to Arlene Foster in Stormont. As the lunch to seal the Joint Report between Commission President Jean-Claude Juncker and Theresa May got under way in Brussels, the prime minister was obliged to take a phone call from Arlene Foster. She told the Prime Minister the deal was unacceptable.

Mrs May had to return to London empty handed. It was a moment of brutal humiliation for the British government.

The DUP had flexed its muscles in the face of its own government, EU institutions and 26 other member states. As a result, all sides went back to the drawing board and produced new language (Paragraph 50) which pledged that the UK would ensure unfettered trade between Northern Ireland and Great Britain in a backstop scenario.

It seemed a moment of immense triumph.

However, according to a new research paper by academics Mary C. Murphy and Jonathan Evershed from the Department of Government and Politics at UCC, this was an ambiguous moment.

"[Arlene] Foster’s torpedoing of the first draft of the Joint Agreement between the UK government and the EU27 represented the peak of her party’s power but also, arguably, its natural limit."

In other words, this would be the one and only time the party would be able to humiliate the prime minister in this way.

Yes, the events of 4 December had resonated well through the base, but it also masked deeper problems facing the party at home.

The work by Murphy and Evershed is part of collaborative three-year project organised by the UK’s Economic and Social Research Council (ESRC) entitled "Between Two Unions: The Constitutional Future of the Islands after Brexit," involving researchers from across the UK and Ireland.

The authors carried out in-depth, confidential interviews with members of the party at all levels on the implications of Brexit.

The resulting portrait is one of a party still coming to terms with what the report describes as a "strategic miscalculation" over its support for Brexit, as well as those key social and demographic changes that were already posing a hard challenge (abortion, gay marriage, changes to the structure of the Assembly).

Having embraced pragmatism and power sharing after the St Andrews Agreement in 2007, the DUP appears to have reverted to what previous academics have described as the traditional sense of siege and anxiety over a Union deemed perpetually under threat by both Irish nationalism and the British government (and now the EU as well).

"The DUP has been consistently mobilised around a deep fear of being 'sold-out' by the British government; betrayed by the weakness of other Unionist parties; and out-manoeuvred by a dangerous Republican enemy," the report suggests.

That narrative is now alive and well within the parliamentary party at Westminster.

Yet, Europe was always a marginal issue. Every European election was about out-voting Sinn Féin, or previously the SDLP, and seats in Brussels and Strasbourg gave the party funding and a platform. On issues such as farming, fisheries, infrastructure and PEACE funding, the DUP was pragmatic to say the least.

It now seems astounding to read the DUP manifesto from 2014.

It stated: "The DUP recognises that the Single Market is one of the European Union's most transformative assets. We want to maximise the economic opportunities that it presents for Northern Ireland.

"As a region of the UK, Northern Ireland is now part of a Europe that is better connected than ever before, by air, rail, sea and online. With better connectivity there is an inherent potential for economic growth, via the free movement of labour, goods, capital and services. [The DUP] wants to help businesses and individuals in our local communities to exploit this potential.

"We are committed to promoting Northern Ireland's highly-educated and high-skilled workforce at an EU level and showcasing our region of the UK as an hospitable business environment within the Single Market."

Arlene Foster’s elevation coincided with uncomfortable change that was already happening to the party. The traditional, evangelical base needed managing as a younger, more modernising and economically liberal wing emerged.

While devolution shifted the centre of gravity to Stormont and away from Westminster, its MPs were, somewhat out of sight, allowed to cultivate links with Conservative eurosceptics.

Senior party figures including Nigel Dodds (below) helped establish Vote Leave, while policy officer Lee Reynolds was seconded to Northern Ireland as the campaign’s regional coordinator.

It is understood a meeting to decide to support the Leave vote lasted 10 minutes. It was seen as an opportunity for the party to let off steam and to burnish its pro-British credentials, but since no one thought the Leave side would win, it would not damage the party’s euro-lite, economically liberal image.

"In this context," says the report, "the DUP’s coming out for Leave was as much a matter of party management and political expediency as of ideological principle".

The DUP’s role in the Brexit referendum is remembered more for its involvement in a series of pro-Leave advertisements in London, than any active campaigning on the ground in Northern Ireland.

This included an advert in the London-based Metro newspaper which cost £282,000 and was paid for through a donation to the party of £435,000 from an obscure organisation called the Constitutional Research Council.

That donation drew suspicions that it was given to the DUP to circumvent transparency rules, as Northern Ireland’s donor secrecy rules are different. Two weeks ago the Electoral Commission ruled that the money was legally permissible.

During the referendum the party had not campaigned heavily in Northern Ireland because its resources were down after the Assembly election earlier that year.

One DUP member told researchers the party was "gobsmacked" when the referendum results rolled in. None of the members seriously thought the Leave side would win.

Rather than wearing the expected mantle of "noble losers", the DUP suddenly had to defend a policy it only half believed in.

And yet, the result was immediately destabilising. The Northern institutions were already fragile. There was an immediate row with the Irish Government over its call for an all-island response to Brexit. Sinn Féin demanded a border poll.

However, the DUP showed its pragmatic side when Arlene Foster signed a joint letter on 20 August 2016 with Sinn Féin’s Martin McGuinness, the Deputy First Minister, on safeguarding the gains of the peace process.

The letter highlighted the need to protect "the border [issue], the all-island energy market, EU peace funding and the need to maintain tariff- and barrier-free trade with the EU, particularly for agri-foods…"

Northern Ireland Executive officials were impressed at the speed with which the letter was drawn up, run through the various departments, and published.

But the bipartisan approach evaporated with the collapse of the Assembly over the RHI scandal and the Irish language.

When, through a fluke of electoral politics, the DUP was gifted the balance of power following the 2017 general election, any hope of avoiding a deeper polarisation in Northern politics melted away completely.

Some officials in Dublin believed that because the party was, on paper, opposed to a hard border it might be a moderating influence on the Tories. That came to nought.

Brexit is now a driver of division in Northern Ireland. Both the DUP and Sinn Féin hold entrenched and deeply irreconcilable views. Nationalists see Brexit as threatening the identity aspects of the Good Friday Agreement, while the DUP sees the backstop as an underhand way of getting a united Ireland.

This has been fuelled by Enda Kenny’s mission to secure a commitment from the EU, now legally watertight, that if a border poll ever resulted in a united Ireland then Northern Ireland would be automatically spirited back into the EU, and by Theresa May’s warning that in the event of a border poll, the pro-union side might not win.

According to its critics, Brexit also potentially allows the DUP to downgrade those aspects of North-South cooperation it has always been apathetic about.

But in its response to the backstop, the DUP has been aided and abetted by Theresa May. From the very get go, the British government has seen it exclusively in terms of a constitutional threat that had to be worn down through alternative suggestions.

One of those suggestions is the UK-wide customs union. It was expressly concocted by London precisely to placate DUP concerns that the Northern Ireland-specific backstop would create a customs border on the Irish Sea.

However, some of the party’s MPs have joined in the ranks of Conservatives who only see the UK-wide backstop as meaning the UK is not properly "out" of the EU.

But an even more significant threat to the DUP has now emerged.

This week a range of business organisations, trade unions and the Ulster Farmers Union (UFU) have come out in favour of the Withdrawal Agreement, even if it raises the prospect of checks on goods going from GB to Northern Ireland.

It is important to stress that for some organisations the Withdrawal Agreement only looks good if the sole alternative is No Deal.

But the fact that the Northern Ireland business community and, in particular the UFU, have always been seen as a natural constituency for the DUP, has made this an extremely uncomfortable moment, and the response from the party has not been subtle.

Sammy Wilson MP, the party’s Brexit spokesman, told the Newsletter that industry figures who had expressed support for the Withdrawal Agreement were "puppets" of the Northern Ireland Office, and that the UFU had been given privileged access to the document before it was published (a claim vehemently denied by the UFU).

At the House of Commons Northern Ireland Select Committee on Wednesday, Jim Shannon MP traded barbs with the Northern Ireland Secretary Karen Bradley, insisting the UFU membership had not been canvassed on the deal.

But there was a clear gulf opening up between the DUP and business, one that has been exploited by Theresa May.

She invited a delegation from the Northern Ireland Institute of Directors to Downing Street on Thursday, as well as representatives from the Freight Transport Association (FTA) for a briefing on the text, knowing it would highlight the gap between mainstream businesses and the DUP.

One operator with a panoramic view of the issues is Mark Huddleston, managing director of both King and Fowler and jheSolutions.

His companies are involved in providing parts and coatings for the aerospace industry, which in Northern Ireland is clustered around Bombardier.

He actually voted Leave because many of his clients are global and he saw the potential in the UK having its own trade policy (family members were also involved in farming and had their own reasons for voting Leave).

But Huddleston is also aware that his company relies both on chemical and metallic inputs, and on end customers, from the EU’s single market.

Any chemicals being sold into the single market, or any goods which use chemicals, must comply with the EU’s REACH directive, which ensures they are safe to use and circulate. Brexit will mean the UK is no longer REACH-compliant - at least until some replacement model is found during the free trade negotiations.

But under the backstop, Northern Ireland companies would be REACH-compliant. They would also be free of any customs obligations when buying and selling into the single market.

"We have to be pragmatic in terms of the outcome," says Huddleston.

"What we have in the Withdrawal Agreement is a good deal for Northern Ireland. There is just some fine detail, but in any deal that’s always going to be the case, and the challenge at the moment is around that east-west relationship in terms of tradable goods.

"We are heavily reliant on REACH-approved chemicals. That’s the attractiveness of the current Withdrawal Agreement as it stands. It gives us the best of both worlds.

"Constitutionally we’ve been through this on a number of times, the Anglo-Irish Agreement, the Good Friday Agreement, the St Andrews Agreement which the DUP built itself, which led to the successful period of the Executive.

"There is opportunity for people to make mischief from it. But is it a genuine [constitutional] issue right now? I don’t believe so. I think the protocols and what’s in the Withdrawal Agreement is very clear in terms of the principle of consent. Now we need to look at the economic and social impacts of this, not the constitutional issue."

But for the DUP both the constitutional and the economic impacts are very real. Diane Dodds MEP says she is exasperated at how things have unfolded.

The Withdrawal Agreement not only disregards what the party believes was a solemn protection in the Joint Report (ie, the new Paragraph 50) for the UK’s internal market, it also will lead to a "real divergence" in the economies of Northern Ireland and Great Britain.

"There are real, real issues," she says, "and the balance is all on the EU’s side. There is no legal effect other than a promise of best endeavours in terms of the UK’s internal market. It will impact on Northern Ireland economically, it can do nothing else.

"The backstop gives legal effect to the EU’s legal order in terms of both customs and in a swathe of regulatory areas. It’s not just a few checks on a few cows."

She argues that under the backstop, the Joint Committee, made up of EU and UK figures, would apply the EU’s state aid regime, meaning London would be unable to subsidise farmers the way it saw fit.

"That’s deeply undemocratic. No politician elected in London or Belfast can alter that. It is the EU’s Joint Committee. We will essentially be handing over manufacturing and agriculture to the EU. Checks mean costs, delays means costs, costs mean business will pass them on to the consumer."

Dodds says the DUP will vote against the Withdrawal Agreement in the House of Commons and that Theresa May’s binary choice of "her deal and No Deal" is a false one.

It is true that just because businesses are warming to the Withdrawal Agreement it does not, of course, mean it will get through the House of Commons. And even if the divorce treaty survives (somehow) in its current form by 29 March next year, there are many tricky questions about how the Irish Protocol will work.

The exact modalities of how to check goods going from GB to Northern Ireland have yet to be fleshed out. Who will manage these checks and where, and what role, if any, will the Northern Ireland Assembly and Executive have?

There will be a role for the overall Joint Committee, made up - it is assumed - of EU and UK ministers and officials, and there will also be a specialised committee for Northern Ireland. But, as yet, Executive officials have had no detailed briefing from London as to how this will work.

This suggests a long period of wrangling over how the backstop will apply in Northern Ireland, if indeed it is triggered. So the party political rancour, with the DUP at its heart, will continue.

The paper by Mary C. Murphy and Jonathan Evershed of UCC suggests the DUP does not have an easy way out of this. "This is reminiscent of the Unionism of old - besieged, insecure, defensive and distrustful.

"From the DUP’s perspective, Brexit simultaneously represents an unanticipated moment of political opportunity and of existential threat."