It was fitting that Arlene Foster resigned the very day that the future EU-UK relationship was finally and formally given its blessing by the European Parliament.
Her career as DUP leader and First Minister was mercilessly bound up with the Brexit withdrawal process, which pitched Northern Ireland right into the thick of the negotiations.
While there was talk about Tuesday's vote which overwhelmingly endorsed the Trade and Cooperation Agreement (TCA), marking a reset in relations following months of acrimony, diplomats in Brussels were not entirely doe-eyed.
They remain concerned about the implementation of the Northern Ireland Protocol and other "irritants", such as the diplomatic status of the EU ambassador in London, and French complaints that their fishermen are being denied licences to fish in UK waters.
A DUP leadership contest, which could install an anti-Protocol hardliner in Stormont, is not welcome at a time when Boris Johnson is floundering over the Downing Street flat refurbishment allegations.
"I don't think that we will suddenly see a new romance," says one seasoned EU diplomat. "I don't think Johnson will suddenly choose this moment to be very constructive. One way of rallying support among the Tories is to take a tough stance towards Brussels."
Brussels is also nervous about Foster’s departure. "This will create uncertainty. What direction will the DUP take? Will they try to find solutions within the Protocol, or will they go completely on an opposition line in order to stave off the threat of the Traditional Unionist Voice? These are things that are beyond the control of Brussels or London."
Or Dublin, where officials are bracing themselves for what happens next. Edwin Poots has been tipped to become First Minister, with the leadership of the party going to another candidate.
While Poots is seen as a pragmatist, he is beloved of the grassroots will want to brandish his anti-Protocol credentials. As agriculture minister he slowed down preparations for the Protocol on the basis that he was politically opposed to it, often to the frustration of officials and ministers in London who would quietly overrule him.
"Would Poots enforce, on a hardline basis, a boycott of the North-South Ministerial Council and the all-Ireland aspects of the Good Friday Agreement?" wonders Professor Jon Tonge, of the University of Liverpool and an expert on the DUP.
"That would have the potential to bring down Stormont and open up another flank. [Boris] Johnson is trying to deal with opposition to the Protocol, with working class loyalists taking to the streets, but he could also be facing a political vacuum with the collapse of the institutions."
Such a scenario ahead of a marching season with fewer Covid restrictions is unsettling to officials in Dublin and Brussels, whatever about London.
"All the assumptions are that, whatever happens next, there will be a more hardline DUP position on the Protocol," says a senior Irish official.
If the MLAs and MPs who brought Foster down want an anti-Protocol leader to corner the anger market well ahead of the Assembly elections, it may backfire.
"Brexit has shaken the Good Friday Agreement and the benign state of politics," says the official, "so if some very hardline position is taken on the Protocol which in turn has a significant impact on the Executive and Assembly, potentially Sinn Féin might take the ball away.
"Arguably the DUP is changing the leader to give them a long run into the next election, so it would be ironic if the act of doing it precipitated an earlier election that they might not be as ready for."
It also raises questions about what a harder position on the Protocol might achieve for the DUP beyond shoring up votes.
The turmoil in the DUP will focus minds in Brussels, but will not change them. The EU and UK are embarked on what an Irish official describes as a "slow but calm" process of working through some 27 areas of contention around the Protocol to see where easements can and cannot be realised.
If the new First Minister and/or leader of the DUP decide to engage in, or at least not disrupt, the fundamentals of that process, then there will be relief all round. But then DUP members might wonder what the heave was for, if it wasn’t solely because of Foster’s perceived timidity on the gay conversion therapy issue.
All this is a reminder of the DUP’s wretched handling of Brexit, an issue for which Foster was singularly unprepared.
Professor Tonge says the party was largely indifferent to the referendum, save for some hardline MPs in Westminster. When Leave won, Brexit was largely ignored at the DUP’s annual conference just four months later.
It was only when Theresa May signed up to the Irish backstop that Foster could unite the party in opposition, but then made the fatal mistake of inviting Boris Johnson to the DUP party gathering in 2018.
"It was all about Johnson becoming Conservative leader and prime minister, but using the DUP as the battering ram against Theresa May," says Tonge.
"There's a certain irony in so many MLAs, and half her Westminster team, now bringing down Foster, because they were just as much cheerleaders for Boris Johnson that day at the DUP conference."
Throughout the Brexit Withdrawal Agreement negotiations the DUP led a charmed life at Westminster, keeping Theresa May in power, despite their opposition to what she was doing.
In Brussels, by contrast, the European Commission and member states had fully adopted the Irish government’s interests in preventing a hard land border.
"The Irish Perm Rep [Embassy to the EU] and colleagues in the [Irish] Department of Foreign Affairs have been incredibly effective over the years in defending the Irish position in Europe," one senior Stormont official told me ruefully one year ago. "When [Michel] Barnier talks about the Good Friday Agreement, it’s as if the unionist perspective isn’t understood."
Northern Ireland Executive officials were involved in the early stages of the Brexit negotiations, but mostly to help out on the mapping exercise which identified which areas of North-South cooperation relied on, or were enhanced by, mutual membership of the EU by Ireland and the UK.
But once the Executive collapsed in 2017 it was a struggle for Northern Ireland officials and politicians to get traction in Brussels, not least because London kept a jealous grip on Northern Ireland issues both in Whitehall and Brussels.
Foster was not a regular visitor to Brussels, and she did not need to travel there to exert her greatest moment of influence.
In December 2017 Theresa May travelled to meet Commission President Jean-Claude Juncker for a lunch to sign off on the Joint Report, the EU-UK political agreement which would lead to the Irish backstop, and ultimately the Protocol.
When RTÉ News revealed that the document contained the possibility that Northern Ireland would remain aligned to the EU’s single market and customs union - in order to avoid a hard border - the DUP responded with fury, and Foster phoned May during the lunch to tell her the party could not support it.
Since May relied on the DUP’s ten MPs for her survival, she was forced into rejecting the deal she was about to sign. It was a humiliating moment for May, but a Pyrrhic victory for Foster.
Foster was relying on London to defend unionist interests, but London had been blindsided by the direction of travel that the EU was taking, at Dublin’s behest, and would frequently struggle to optimise its position in the negotiations.
When London needed to get over the Irish hump to keep the negotiations on track, May had to accept painful compromises. That is, until she unambiguously rejected the first draft of the Withdrawal Agreement, which would have placed - had the backstop been used - a border on the Irish Sea.
Yet when May successfully negotiated the UK-wide customs union, to explicitly take account of both unionist and industry concerns, the DUP rejected it.
"That solution was very unionist-friendly," says one senior official. "The DUP as a party has to answer the question, why did they not embrace the Theresa May deal? Even when London said, whatever else happens, we will minimise disruption by maintaining maximum alignment. That lost May supporters in the Conservative Party, but it was a determined gesture to try to keep the DUP on board. It didn’t work."
By October 2018 the UK-wide customs union was almost a done deal. Foster travelled to Brussels to meet Michel Barnier, the EU’s chief negotiator, and the Dutch, French and German ambassadors, as well as Ireland’s ambassador Declan Kelleher.
She stuck to platitudes about a "sensible" Brexit, and no border on the Irish Sea. She also warned of "blood-red lines" and "catastrophic" economic consequences for Northern Ireland if there were any trade barriers on the Irish Sea.
With no creative thinking about how to avoid a land border, save for the ill-starred "alternative arrangements" idea, Foster’s entreaties about unionism and Northern Ireland’s place in the United Kingdom largely fell on deaf ears.
"There was zero chemistry between Foster and the Commission," recalls one official close to the discussions.
With Boris Johnson’s Protocol now in place, the Irish Government is, ironically, taking a more proactive role in quietly lobbying capitals on its difficulties, and facilitating contacts between those capitals and stakeholders in Northern Ireland.
This is being done alongside the work of the EU-UK Joint Committee, which is doing its own outreach to business, logistics and farming groups in the North under the direction of Maros Sefcovic and David Frost.
While the European Commission is the lead actor in the Protocol negotiations, Dublin has been trying to get member states attuned to the complexities of Northern politics, both to urge capitals to be as pragmatic as possible, and so that the middle ground in the North feels Europe is listening.
This week Minister for European Affairs Thomas Byrne travelled to Berlin to meet his German counterpart Michael Roth (who has close ties with President Michael D. Higgins), as well as Alexander Lamsdorff, a Liberal MP on the Bundestag EU Affairs Committee, and Franziska Brantner, a Green MP and the party’s spokesperson on Europe.
Both politicians could well be part of the next German government from September.
In February Byrne encouraged Ana Paula Zacarias, the Portuguese Europe Minister to engage with Northern Ireland stakeholders (Portugal holds the rotating EU presidency) and his officials facilitated a Zoom meeting with the Centre for Cross Border Studies in Armagh.
The French Europe Minister Clement Beaune, and his Finnish counterpart Tytti Tupparainen, are also expected to travel to Ireland in May or June.
The issues at the heart of the Protocol were also the subject of a recent meeting between EU ambassadors to Ireland and a cross-section of community figures from Northern Ireland, hosted by the Glencree Peace and Reconciliation Centre in County Wicklow.
"We have always said this is a question of securing the EU’s single market, but also making the Northern Ireland Protocol work," says one ambassador who attended the Glencree meeting.
"We very much want the [European] Commission, within the negotiations with Britain, to find a way to get the Protocol going. It's been a long process to get there and this is the best way we have."
Dublin’s outreach is a delicate balancing act. Large member states like France and Germany have concerns that if the Protocol is not implemented properly, or if there are too many shortcuts, then Northern Ireland will become a grey zone which permits the entry of illicit or unchecked goods into the single market.
Ireland is also mindful that the statecraft required to ensure no hard border needs to be updated.
"Five years ago the focus was no hard border," says one minister. "That was a really important strategic objective for this country, and that has been solved by the Protocol, which is here to stay. But now we need to focus on what the situation is like on the ground in Northern Ireland, and getting Europe to engage there as well."
But the government is aware that it runs the risk of being seen as acting as an advocate for the British government in how the Protocol is managed. Indeed, there were mutterings in Brussels in February, especially after Ireland lodged its protest over the invoking of Article 16, that Ireland somehow wanted to become "equidistant" between the EU and the UK on the Protocol.
"Engagement is helpful," says a senior Irish source. "We would have wanted to do it anyway, but there was concern in the Commission that other capitals might misunderstand the role we were trying to play."
One EU diplomat says of the Irish outreach: "It’s a smart move and they’re very good they're doing that. For a lot of countries they see everything through the prism of, is there a risk to the single market because they're not implementing the Protocol?
"On the other hand, we're not deaf to what's happening on the ground, and we're not blind to pragmatic solutions when it comes to minimising the risks in Northern Ireland."
But those solutions are still not in sight. London and Brussels have set up an Agri-food Forum, comprising officials from DG SANTE, the Commission’s food safety and animal health directorate, and Defra, the UK department of agriculture, as well as officials from the Cabinet Office.
The forum joins the ever-expanding structure of committees all now exploring ways to manage the Protocol. It will be a long process, and a full blown negotiation between the EU and UK about a new veterinary agreement, which would do away with some 80% of checks and controls on the Irish Sea, has not started yet - if it ever will - because both sides are holding absolutist positions.
How the process to replace Arlene Foster plays out will make the process easier or harder.
"If the focus [of the EU UK technical talks] is on specific problem issues, then some of them can be managed or mitigated," says a senior Irish official. "But if there's a more fundamental determination that the Protocol by its nature is offensive, then we obviously have a different problem.
"Because then you can't talk about the Protocol in isolation from the bigger problem, which is Brexit. So you're back to square one."