Next week will be another milestone in the long road to resolving the Irish border issue. On Wednesday the College of 27 EU Commissioners will sign off on a draft legal text which is supposed to translate December’s deal paving the way to Phase II of the Brexit negotiations into a legally binding form.

The text will be circulated among officials from the 27 member states and will then be subject to further negotiation with the UK.

It will ultimately be folded into the Withdrawal Agreement, the formal treaty which comes into effect on 29 March 2019, the day Britain leaves the European Union as a full member.

While the text will cover the other two issues agreed back in December - the financial settlement and citizens’ rights - the critical component will be how the deal on the Irish border is managed.

The Joint Report, as December’s deal is known, has two key paragraphs on Ireland. Paragraph 49 is about how to avoid a hard border on the island of Ireland, and Paragraph 50 is about how to avoid a border along the Irish Sea.

Belying that simple formulation, however, are a raft of contradictory interpretations and competing gravitational forces. To say that how those political paragraphs are given legal clarity has the potential of drastically altering the course of Brexit - and Theresa May’s knife-edge survival - would not be an overstatement.

It’s worth recapping what the paragraphs mean.

Paragraph 49 says that there are essentially three options to avoid a hard border.Britain’s preferred approach is that the border will simply dissolve by means of a deep and comprehensive free trade agreement between the EU and UK (Option A).

If that doesn’t work, then Britain will propose specific solutions: these include using technology, trusted trader customs concessions, cross-border SME exemptions on customs declarations and so on (Option B).

If neither of these work, then Option C comes into effect: the UK will ensure full alignment of the rules on both sides of the border as they pertain to the EU’s single market and customs union. To many, this would mean Northern Ireland remaining de facto inside both EU structures.

Paragraph 50 spells out that, if Option C comes to pass, there would be no barrier between trade flowing back and forth between Northern Ireland and Great Britain. This was the paragraph that was added to the original text in order to placate the DUP, on whom Theresa May relies for survival.

The ink was barely dry on the December agreement when its glaring contradictions became obvious.

If there was no border on the island of Ireland, then the only way to stop goods from Great Britain that were not compliant with EU regulations and standards from flowing into the single market via the Republic of Ireland would be to impose checks at Northern Irish ports and airports.

But Paragraph 50 appears to preclude that.

In that case, the only way to protect the integrity of the single market would be if the UK as a whole were aligned with the EU single market and customs union.

But the Conservative Party, and the DUP, are - for the most part - dead set against such an arrangement, because it would prevent the UK having an independent trade policy post-Brexit.

How will this circle be squared when the political fudge of December is converted into a binding and unambiguous legal construct in February?

This is where there are furious competing forces that will yet shape what next week’s text looks like.

Let’s start with one of the more straightforward contradictions - Paragraph 50.

It reads: "In the absence of agreed solutions…[ie, if Option C comes to pass], the United Kingdom will ensure that no new regulatory barriers develop between Northern Ireland and the rest of the United Kingdom, unless, consistent with the 1998 [Belfast] Agreement, the Northern Ireland Executive and Assembly agree that distinct arrangements are appropriate for Northern Ireland."

Both Dublin and the European Commission Task Force under Michel Barnier regard this as a commitment by the United Kingdom to the DUP, and not an EU commitment to the DUP. In other words, if there is a contradiction there once Option C (ie, full alignment north and south) comes into effect, then it will be up to London to sort it out.

When we move on to the other contradictions that run through the December deal, we get into the problem of sharply differing interpretations of what alignment means.

The UK believes that alignment is a voluntary act. The UK will decide itself to align its policies with the EU rulebook if it is appropriate to avoiding a hard border.

London regards the alignment as like train tracks: parallel, but not identical. Furthermore, it believes that, if Option C is a must, then it should be piecemeal and flexible. In other words, only those areas of North-South cooperation which have been proven empirically to need EU regulations to work on both sides of the border should require alignment (the UK often refers to the Single Electricity Market as the classic example).

Also, alignment should be about outcomes and not about following EU rules to the letter.

Dublin sees alignment as something entirely different. Last autumn, officials on all sides were locked into the so-called ‘mapping’ process, whereby 142 areas of North-South cooperation were first identified by the UK, and then analysed by the European Commission Task Force to see where that cooperation and EU rules collided.

According to Dublin (and Brussels) that collision was across the board. The only way, therefore, for that North-South cooperation to emerge unscathed by Brexit was if the EU rules that facilitated it continued wholesale on both sides of the border.

This clashing interpretation has not been resolved.

And the debate within the Tory cabinet, which seemed to have found an uneasy truce in Chequers this week, reveals just how far apart both sides are.

Back in December, some Irish Government ministers had an optimistic take on the apparently contradictory Paragraphs 49 and 50. They felt that if the North and South were aligned, and if there were to be no barriers between the North and the rest of the UK, then the logical conclusion was that the deal would actually bind the entire UK more closely to the EU.

But noises from the British Cabinet ever since suggest that, rather than remain close to the EU regulatory sphere, the UK will at best embark on ‘managed divergence’ or at worst (from an Irish point of view), diverge almost completely and do it sooner than later, so that Britain can strike free trade deals around the world.

This is because if the UK had to stick to the EU rulebook, then it would limit its room for manoeuvre when negotiating trade deals elsewhere.

The fact that the December deal must now be codified into a legal text suggests that these contradictions now face a reckoning.

Much will depend on how detailed Wednesday’s text is. For the Irish government, the key word is "operationalise". Dublin wants Britain’s Option C guarantee - the backstop - to be operationalised in the legal text. In other words, how exactly will "maintaining full alignment" (as Paragraph 49 states) actually work in practice? How will it be pinned down in law in such a way that respects the EU rulebook across the board?

Dublin wants as much detail on Wednesday as possible so that these issues are nailed down, and not kicked down the road.

Furthermore, to Dublin (and the EU) the alignment must be asymmetrical. In other words, there cannot be a situation where every time the EU introduces new laws it has to look over its shoulder to make sure they’re aligned with Northern Ireland’s rules, just because Northern Ireland has to stay aligned to EU rules when Brussels brings out new laws.

"That’s not the world we’re living in," says a senior EU official.

Northern Ireland, in other words, would have to remain compliant with existing and new EU rules if Option C is to work.

The UK, on the other hand, would prefer Wednesday’s text to say as little as possible on Ireland.

Throughout the autumn, London argued that the border issue could not be solved because it was a Phase II issue, in other words, that it was in the realm of the future trading relationship. Dublin argued that while the border may not be solved in Phase I, there had to be sufficient progress, and a guarantee from the UK so that Ireland wasn’t taking a leap in the dark.

London still believes that Options A and B are sufficient to avoid a hard border. It wants those options to form part of the legal text and to be written into Withdrawal Agreement.

Ireland, and the European Commission, on the other hand, believe that Options A and B more properly relate to the future trade relationship. It is unlikely, therefore, that any language relating to Options A and B will be looser and not fully binding legally.

The other question is the mapping exercise.

This huge body of work is essentially the pathway which led Ireland (and the Task Force) to the conclusion that to properly safeguard North-South cooperation, there should be no regulatory divergence on either side of the border.

Through the so-called high-level dialogue dealing with Irish issues, the chief UK negotiator Olly Robbins and his counterpart Sabine Weyand (Michel Barnier’s deputy) have been trying, inconclusively according to EU sources, to figure out what to do with the fruits of the mapping exercise, whether it should be published in full as an annex to the legal text, or whether it should remain unpublished (it’s understood there remain some aspects of the mapping that are not complete).

In general, the UK wants as little about Ireland in the draft legal text as possible. It’s understood senior British officials have argued that the deadlock in Stormont means that the text should be cautious/minimalist in order not to inflame tensions.

Dublin would most likely argue that Theresa May should not use the Stormont issue, nor, more critically, her reliance on DUP votes, as an excuse to backslide from what was agreed in December.

The other issue is where the alignment backstop (Option C) would end up.

Fianna Fáil has raised the alarm over suggestions that Options A and B would be kept in the body of the legal text, while Option C would be put into a protocol. This, says the party, could amount to a watering down of the alignment option.

My understanding, however, is that the EU has long regarded a protocol as the best option for the simple reason that EU treaties tend to put member state-specific issues into legally binding protocols and not into individual chapters in the main treaty.

Ireland is no stranger to such protocols: the Lisbon Treaty contains protocols to the effect that neutrality, abortion and taxation will not be affected by the Treaty as they are areas of national competence.

The Common Travel Area is also handled in Lisbon under Protocol 20. The UK’s historical opt outs on justice and home affairs, and on the euro, are also handled by protocols. One Irish source said that the placing of Option C into a protocol will be fine "as long as it’s legally binding, which it will be."

But the tension over the text is not two-way, between Dublin and London, but three-way. Other member states are watching this issue closely, but for different reasons. French officials, in particular, are reportedly skeptical that Option C, ie full regulatory alignment to avoid a hard border, can actually work.

France, and other member states, will want to know that a fudge on the Irish border does not give rise to wholesale smuggling of non-EU compliant animal products (either live or processed) into the territory of the single market via the Republic.

For that reason, member states are likely to want more - and not less - detail in Wednesday’s text.

The European Commission Task Force, which, alongside the Commission’s legal services, is in the driving seat in drawing up the draft text, will be of the view that Option C needs to be fleshed out, or "operationalised" in the jargon.

This is not only because the Commission has, since the very beginning, worked closely with Dublin on the border issue, but also because it wants to flush the UK out on its overall intentions. By getting the British to engage on the detail of Option C (this is, don’t forget, a draft which will be subject to intense EU-UK negotiations), the Task Force will hope that it will concentrate London’s mind on its overall intentions on the future trade relationship.

Hard Brexiteers are furious that their vision of being out of the EU should be somehow shackled by the Irish border. Their arguments range from assurances that technology and "good will" will remove any hard border, to a view that the entire issue is an artificial ruse concocted by an unholy alliance of Remainers and the Irish Government.

Dublin is sticking to its guns, but it is reluctant to appear too adversarial towards London. That’s why in recent weeks both Taoiseach Leo Varadkar and Tánaiste Simon Coveney have suggested that a deep free trade agreement could be a way to solve the border issue, and that Ireland would be Britain’s friend in the negotiations.

But Dublin’s preferred free trade options sometimes shift. In Davos Leo Varadkar described his preference as "Norway Plus", which would be akin to the UK staying in the single market and customs union, i.e. not having a say in the rules, abiding by the four freedoms and paying into the budget (political non-runners for Theresa May).

He also said that the UK could get a bespoke deal. The UK was entirely different to Canada and Norway, so it should get something in between (something Theresa May has long advocated, although with not much detail).

Will Ireland still be able to block the negotiations if it looks like the bullet-proof guarantee of no hard border meets insurmountable challenges, either through the UK backing off from its guarantee or other member states simply not trusting that no checks on the Irish border can properly guarantee the integrity of the single market?

So far, the unity of the 27 has held, but that unity has not been challenged by the conflicting interests of a trade negotiation.

As far as the Withdrawal Agreement is concerned, it will be reached not by unanimity but by a qualified majority vote. But such a vote going against the wishes of Ireland is, according to one senior EU official, unlikely.

"There are 27 around the table. Without the Irish signing up to this agreement there is no agreement," he says.

"Even if in theory we might agree to do this with a qualified majority, nobody thinks about this option. Everybody understands that we the 27 have to do this together, and therefore there’s no chance that we would be voting down Ireland at the end of this process. That’s not going to happen."

So all eyes will be on the legal text due on Wednesday. How that text "operationalises" Option C, will, depending on the detail, most likely constrain the ambitions of Brexiteers by forcing Theresa May to confront entirely unpalatable options as far as half her cabinet - and the DUP - are concerned.

The political crunch is that the closer Theresa May is encouraged to cleave to EU structures, through alignment or a customs union or the jurisdiction of the European Court of Justice, the greater the risk of a coup by hardline Brexiteers.

A letter urging her to tilt in the opposite direction was signed by 62 Eurosceptic Conservative MPs last week, enough to trigger a leadership challenge.

The hope is that some, or most, of the legal text could be signed off by the UK and EU in time for the European Council on 22 and 23 March. But so precarious is Theresa May’s position that anything could happen before then.