The fate of Northern Ireland is once again captive to the internal dynamics of the Tory Party, continuing an ignoble line going back to David Cameron and well beyond.

Boris Johnson used the Northern Ireland Protocol to launch his own leadership bid in 2019. With his leadership now in crisis, Johnson is not beyond leveraging a hardline position on the Protocol to stave off a political assassination - that is, if he is able to focus on it.

But if regicide it is, then contender Liz Truss, the UK's fifth Brexit negotiator in as many years, could be tempted to calibrate her Protocol position in the service of leadership ambitions.

Ahead of her first meeting with her EU counterpart Maroš Šefčovič, Ms Truss struck an optimistic note: "There is a deal to be done that protects peace in Northern Ireland, defends our Union, and maintains the integrity of the United Kingdom and EU. But it will require a pragmatic approach from the EU."

But any leadership ambitions could complicate both the outcome and timeline of the deadlocked Protocol talks. They were due to wrap up by Christmas, then February, but if Johnson holds on until May there is the possibility that the Protocol stand-off could stretch well into the autumn.

Liz Truss and Maroš Šefčovič met at Chevening House in Kent this week

"The general feeling is not very optimistic," says one EU official familiar with negotiations. "Or of not expecting very much, but with a heavy heart because we've been putting a lot of work into this, and we can't see the situation getting fundamentally better anytime soon."

This will be a challenge for Dublin, and for the Biden Administration. "The big strategic question for Dublin, for Brussels, for Washington is: How much do they invest in trying to make this work until Johnson is replaced?" says Paul McGrade, senior counsel with the Lexington political consultancy: "Aren't we now looking at paralysis? Isn't that the real risk until Johnson has a successor?"

'The Protocol in its various incarnations was the messy compromise'

When it comes to the Irish question paralysis has, indeed, been the driving factor since the Brexit referendum. The Conservative Party has never been able to reconcile its internal Brexit factions, nor to reconcile any version of Brexit with the complexities of Northern Ireland, as articulated by Brussels and Dublin.

"Northern Ireland was always the point at which the inconsistencies or the contradictions of the hard Brexiteers position collided," says a senior Irish official.

"The Protocol in its various incarnations was the messy compromise. Now Truss has just become the latest holder of the bowl of poison because those contradictions are exactly the same."

Lord David Frost, her predecessor, suddenly resigned in December, just as the negotiations were reaching a critical stage. His departure has reshuffled the deck and left observers trying to fathom his motives and how ominous his presence will be as the new hero of the hard Brexit European Research Group (ERG).

While Frost was thought to have been dismayed at the lack of support from Downing Street for his hardline demands on removing the European Court of Justice (ECJ) from the Protocol, his resignation letter reflected a broader discontent over Covid restrictions and a lack of enthusiasm in Whitehall for diverging from the EU’s regulatory orbit.

"The challenge for the Government now is to deliver on the opportunities it gives us," Frost wrote. "You know my concerns about the current direction of travel. I hope we will move as fast as possible to where we need to get to: a lightly regulated, low-tax, entrepreneurial economy, at the cutting edge of modern science and economic change."

Lord David Frost resigned in December as the talks reached a critical stage

Officials in Dublin and Brussels were struck by how little Brexit featured in the letter, and have speculated Frost jumped ship in order to preserve his own career prospects.

"He knew that he'd have to face the music at some point on the Protocol," says an EU official. "He's smart, so he chose to jump at a time of his choosing, when he was still unscathed."

Now as poster boy for hard Brexit and anti-Covid restriction sentiment, Lord Frost could be a thorn in Truss’s side if she takes a more flexible approach to the Protocol.

Frost also left Johnson with the headache of re-allocating the various Brexit tasks. As well as running negotiations on the Protocol and representing the UK in the EU-UK Joint Committee, Frost was co-chair of the Joint Partnership Council, managing the Trade and Cooperation Agreement (TCA); head of the Border Delivery Group, tasked with ensuring ports and borders were ready; and steering the new Brexit opportunities unit.

With Frost gone, it’s not clear if all of these will be shunted over to the Foreign Office, and whether or not Truss will have the bandwidth to ensure her department can acclimatise to the new responsibilities at speed.

Irish officials have taken comfort from the fact that as foreign secretary Truss will need to take the broader view of Britain's European and global interests

Maroš Šefčovič has made it clear Truss will be his interlocutor, but if she is globetrotting every week then the schedule of Protocol meetings in London and Brussels, as arranged with Frost, will run into trouble.

"There are lots of debates in the UK about whether she's been handed a poisoned chalice, or whether this is a chance for her to build back the Foreign Office, which has seen a rather diminished role over the last decade," says Jill Rutter of the think tank UK in a Changing Europe. "They didn't seem to have thought about the consequences of it."

During most of the negotiations on the withdrawal and the future relationship treaties Truss was international trade secretary. Ironically, she played no part in the EU-UK free trade negotiations (Number 10 kept firm control of both treaties). She will now have to master the detail of the Protocol and the TCA (the eurosceptic MP Chris Heaton-Harris will support Ms Truss in the talks).

Irish officials have taken comfort from the fact that as foreign secretary Truss will need to take the broader view of Britain’s European and global interests, in contrast to Frost, who’s main concern was ensuring a hard Brexit.

"Frost was exclusively the minister for Brexit and EU negotiations," says a senior Irish source. "If someone said, this is not going to play well for US relations he could, to a certain extent legitimately, either not care or not have to deal with that."

As the figurehead of "Global Britain" Truss will have to care. She made a point of briefing UK journalists that she had contacted foreign ministries across the EU when she was appointed. Sir Tim Barrow, currently political director at the Foreign Office with responsibility for EU affairs, and a former UK ambassador to the EU, will likely have a more prominent role.

There is also the suspicion in Brussels that Truss will prefer to peel off member states on bilateral issues

Truss faces a number of choices. Is she more inclined to get a deal on the Protocol by the end of February, leaving her free to project Britain’s role in the great geopolitical challenges?

Or, does she prioritise eurosceptic backbenchers in order to enhance her leadership credentials? She will need the ERG to get into the final ballot in a leadership contest, but if she gets to that point, she will no longer need them.

"With big issues over Russia, Ukraine, China," says Jill Rutter, "does she really want to get bogged down in weeks and months of detailed negotiations over medicines, customs rules, checks - all those detailed things of the Northern Ireland protocol?

"Or does she want to move to a swift agreement so she can get on with…working with the EU on a whole bunch of other issues where the UK and European nations have a lot of common interests?"

The problem is that the structures are not yet in place for any formal EU-UK cooperation on foreign and security policies, largely because Frost resisted putting such a relationship on a formal footing.

There is also the suspicion in Brussels that Truss will prefer to peel off member states on bilateral issues (the UK has already sent a small number of soldiers to help Poland tighten its border with Belarus).

"It might be that things change, but there are no tools to do it at this stage," says an EU official. "The relationship with the UK is still very much seen through the prism of the post-negotiation period. We don't think of the relationship with the UK as we do with the US. That's probably where someone like Truss wants to get to - but we're not there yet."

Member states would probably want to get there too. "There is a common-sense willingness and political will to engage with the UK in the [EU Common Foreign and Security Policy] and having the UK as a partner," says one EU diplomat. "It's simply been blocked out by the noise of the TCA, the Protocol, and the fact that the Brits say they don't want to have a formal agreement."

If Truss has her eye on the prize of enhancing EU-UK cooperation on Russia, China, climate change and so on, the incoming French presidency of the EU has made it clear that a pragmatic approach to resolving the Protocol will help.

One EU source suggests that so long as Britain trashes the relevance of the EU on the global stage then an improved strategic relationship will be off limits.

"There are several aspects we have to address before we get to a normalised relationship…," says the source. "The first is the Protocol. For more than one year the UK has not implemented it. The EU has been patient first, constructive second in its proposals, but we have no solution for now."

There remains a 'sizable distance' between both sides on the NI Protocol issue

Truss gave a grudging acknowledgement of those proposals in her Sunday Telegraph article last weekend in which she predictably took a hardline on the Protocol and on triggering Article 16 (she wrote that Northern Ireland should not be treated as if it is in the Single Market, which is actually the entire basis of the Protocol).

Weary EU officials, who have endured years of UK positions being presented first through pro-Tory newspapers, were stoical. Dublin also detected signs of hope in that Truss explicitly singled out problems - such as the movement of pets from GB to NI, and the accessibility of Kosher food for the Jewish community - which would certainly be solvable in the negotiations.

Truss’s first move - to issue an early invitation for Šefčovič to spend the night in Chevening House, the Foreign Office’s grace and favour pile in Kent - was a contrast to the pizza and sandwiches provided by Lord Frost in a Cabinet Office basement.

But will a softer style lead to a deal by the end of February?

Much will depend on her leadership ambitions. Truss has relished her boosterism role as trade and now foreign secretary and will present herself as a born-again Brexiteer happy to wave the flag for Brexit - but also to get deals done.

Triggering Article 16 would risk a sharp response from the EU, with the prospect of a trade war

She has already held a first meeting with the Minister for Foreign Affairs Simon Coveney. "It was quite warm and friendly," says one source briefed on the encounter. "But the substance remained pretty much the same, with the UK side harking back to the [July UK] Command Paper, talking about very significant changes to the Protocol, the Article 16 threat being bandied about in the background."

How she manages the contradictions and risks will be key. Her Sunday Telegraph article was a restatement of the UK position under Frost, and a demonstration to the ERG (and DUP) that she was biddable. But in advance of a leadership challenge, she will not want to take on unnecessary risks.

Triggering Article 16 would risk a sharp response from the EU, with the prospect of a trade war at a time of rising inflation, increased taxes and national insurance contributions, and energy prices in the UK.

This is the quandary Truss would face.

"She might be reluctant to sign up to any deal that will be promptly ripped apart by the ERG, and she would be castigated for selling out," says one EU diplomat.

But in negotiations, style and tone can count for a lot. There is still a sizable distance between both sides. London had softened its demand that the ECJ be removed entirely from the Protocol with UK officials conceding in December that the court could adjudicate on points of EU law, but any dispute between the EU and UK over the operation of the Protocol should be handled by international arbitration.

There is no indication that the EU is prepared to move in that direction.

Before the talks broke up in December, the EU’s October proposals remained the main subject of negotiations. While Brussels has started the procedure to change EU law so that medicines can flow freely from GB to Northern Ireland, there is still no breakthrough on customs and agri-food (SPS) checks and controls.

In her Sunday Telegraph article, Liz Truss wrote of a "common-sense solution" whereby goods going to the Republic via Northern Ireland should be checked and those staying in Northern Ireland should not. "That means no checks or documentation for goods moving from Great Britain to Northern Ireland and staying there," she wrote.

"That gets right to the nub of the whole Protocol," says an Irish official, "because if that were theoretically possible, everyone would say fine. But the question is, how are you going to do it? Thus far the best they've managed to come up with is that traders will tell us. Obviously, that's not going to be enough for the EU side."

'Northern Ireland potentially has economic benefits to reap from all of this if we settle the Protocol'

The EU believes this will not provide the level of legal and physical certainty that the goods crossing its external border are being properly managed, or at least a significant percentage of those goods that are declared to be only going to Northern Ireland are being checked.

"In other words, you're not systematically checking everything," says the official. "But you do have the right to check stuff to verify that no-one is taking advantage of a grey area. They’ve never really said how that would be done."

The Commission insists its October proposals will significantly reduce the level and volume of checks and controls, both for customs and SPS consignments. London says these figures are unreliable and there will still be a chilling effect, meaning smaller companies will still find it too expensive or burdensome to ship to Northern Ireland.

The deadlock is there because so long as London insists that no goods moving within the UK’s own territory (and staying there) should be checked, then a fuller discussion with the Commission has not been possible.

"If the idea is that the energy of the moment and Truss’s arrival are going to create a better atmosphere," says an Irish source, "then the question is: Will that allow for the unlocking of conversations that haven't been possible? I think the scope is pretty limited. But we would at least move into a better place."

In the weeks before Christmas the UK team was seeking to reach an agreement on some aspects of the Protocol, and to kick the more difficult aspects into the long grass. This has been rejected by the Commission.

"Northern Ireland potentially has economic benefits to reap from all of this if we settle the Protocol, because it will have access to the single market and the British market," says an EU diplomat.

"But investors will only act if there's certainty. If you kick the can down the road then investors will sit back and wait. It’s not good for the Northern Ireland economy. Meanwhile, the Protocol is deeply affecting the bigger relationship between the EU and the UK."

If Liz Truss is determined to do a deal, it could come down to how it’s presented. Truss has unabashedly trumpeted the UK-Australia free trade agreement, even though the government’s own figures indicate the benefit to the UK economy will amount to between 0.01% and 0.02% of GDP.

Truss emphasised publicly and privately that the UK would like to do a deal sooner or later

"With the right packaging and the right presentation, she could present it as a big victory," says the diplomat. "It would be up to her how best she wants to handle this."

Don’t forget Boris Johnson, who will have to give his blessing to any deal. He has until May to save his position. That could make him risk-averse and too distracted to devote too much attention to the Protocol.

Johnson has also been contradicting any notion that he was ultimately a softer touch than David Frost.

"Frost repeatedly said that while everyone thought he was the hard man, actually Boris [Johnson] was the most hardline of all on the sovereignty and ECJ stuff," says a well-placed Irish source.

"That’s true insofar as anyone who has engaged with Boris in calls he's had with other prime ministers and contacts with the Taoiseach. On the substance, he was very hardline and he also went out of his way to say: everyone thinks Frost is the hardman, but take it from me, I'm every bit as hard."

In the event, the meeting in Chevening House appeared to be a get-to-know-you affair - plenty of warm vibes and appreciation on the EU side for the hospitality. But no real progress.

"The atmosphere was warm, cordial, very friendly," says one EU diplomat briefed on the meeting, "with Liz Truss emphasising publicly and privately that the UK would like to do a deal sooner or later. But when it came down to the specifics the UK side quickly retreated back to fairly traditional positions, more or less based on the demands of the Command Paper."

Discussions focused on customs, SPS checks, state aid and governance, with the UK side emphasising sovereignty, demands for movement on the ECJ, and an expectation that there should be no checks on any goods clearly going to end-users in Northern Ireland.

"There were patient explanations from the EU side as to why some of this could not be achieved," said the diplomat.

Truss and Šefčovič will meet again on 24 January, and the EU believes Truss wants to do a deal. There was no deadline agreed.

Should things drift into the spring, EU officials are concerned that a Tory leadership contest, and even the prospect that it may take considerable time to re-establish the Northern Ireland Executive, do not bode well.