'I am not trying to provoke,' said Michel Barnier

"You should know me well enough to know I don't bluff," the EU's chief Brexit negotiator told me this afternoon.

To another journalist, Michel Barnier added: "I am not trying to provoke. Not trying to create shock waves. It was the UK which decided to leave. There is no arrogance here. I have immense respect for the UK."

Yet he did provoke, he has created shock waves and history will tell if he was bluffing.

The document released today is the legal interpretation of the agreement on the divorce between the EU and UK come to in December.

:: Defiant May rejects EU's plan for NI border


May: No PM could agree to EU demands

The EU side says it contains "no surprises" and faithfully installs in a draft legal text the commitments made in December.

The problem is that those December commitments were woolly, somewhat contradictory and contained one key point which was politically explosive then and was sure to come back to bite them at some point.

It was on the Irish border issue: specifically the idea that if no other feasible solutions could be found to solve the border conundrum (read on for detail) then "the United Kingdom will maintain full alignment with those rules of the Internal Market and the Customs Union which, now or in the future, support North-South cooperation, the all-island economy and the protection of the 1998 (Good Friday) Agreement".

The problem for the British now is that they believe the EU legal interpretation of those words in the December agreement have nuanced differences.

The new legal text says: "A common regulatory area comprising the Union and the United Kingdom in respect of Northern Ireland is hereby established.

"The common regulatory area shall constitute an area without internal borders in which the free movement of goods is ensured and North-South cooperation protected in accordance with this Chapter."

The British interpretation of that new wording is that the EU is effectively asking the UK to be prepared to annex Northern Ireland rather than the whole of the UK aligning with EU legislation.

Northern Ireland would, if no other solution for the Irish border question was found, align with the Republic of Ireland (and by extension the whole EU) thereby moving the border to the Irish Sea.

:: Analysis: No options acceptable for Irish Brexit border

NI border issue being exploited - Johnson

Responding to the new document, Theresa May said: "The draft legal text the Commission have published would, if implemented, undermine the UK common market and threaten the constitutional integrity of the UK by creating a customs and regulatory border down the Irish Sea, and no UK prime minister could ever agree to it."

The December agreement was a fudge to allow talks to move on to discussion of the future relationship; tricky issues were kicked down the road and weight was given to other solutions which, to date, have not proved to be workable.

Option "A" as it became known, was a rich free trade agreement which would remove the Irish border issue.

Option "B" was to provide technological solutions to ensure the border remained invisible despite there being different regulations on either side of it.

The UK still believes that one of those two will happen.

Yet the EU has described option "B" as "magical thinking" and option "A" as pretty close to the "have your cake and eat it" scenario - "an illusion".

So, says the EU, option C (Northern Ireland alignment with the EU) must be contained in the legal text, just in case.

Sky obtains explosive memo from Boris Johnson

"It can always be deleted in due course," Mr Barnier said.

For now, because option A and B remain only aspirations, option C gets greater legal weight in the draft document.

Mrs May knows the Irish Sea border scenario (the consequence of the effective annexing of Northern Ireland) is roundly unacceptable: to the Democratic Unionist Party in Northern Ireland, who prop up Mrs May's government in Westminster; to Conservative backbench Brexiteers, but more fundamentally too - it would effectively break up the UK - a non-starter.

Does that mean that the whole of the UK remains in the customs union and single market?

The UK government has explicitly and repeatedly said that the UK will not be in "the" customs union or "a" customs union or the single market.

PM faces fresh Brexit rebellion in the Commons

Option A - a rich, bespoke trade agreement - is years off (the Canada deal took nearly a decade).

So that's probably why every effort is now being made to find a technological solution - option B - as illustrated in the Boris Johnson letter leaked to Sky News.

Remember though, this is just a draft.

Under normal negotiating circumstances it wouldn't have been released.

But in the interests of transparency (and probably to focus minds and chivvy things along a bit) the EU has released it.

By the time it is finally signed - probably in October, the hope is that the UK will have made real the "magical thinking" for technology on the Irish border.