Image copyright Reuters Image caption Irish deputy PM Simon Coveney shakes hands with EU chief negotiator Michel Barnier

DBP. Let's have a new one, a new acronym of course, because Brexit has been nothing if not a journey through collections of syllables that once might have seemed unfamiliar to even political aficionados, but now trip off the tongue.

DUP? Easy one, the Tories' Northern Irish allies.

ERG, obvious too, the European Research Group - the Brexiteers' club.

Then there is NCP, what was once upon a time Theresa May's plan for customs, the IP, the implementation period, the departure lounge after Brexit, and so on, and so on, and so, until we all lose the will to live.

If you are still with me then let's introduce 'DBP', because on a very odd day in Westminster, it's the phrase I have heard almost more than any other - difficult but possible.

Conversations and Contradictions

Without being one of the genuinely tiny group of people who know exactly what has been put on the table, and exactly what concessions and compromises are being wrangled over, you join me, with many others in Brussels and Westminster, in the territory of informed guesswork.

One government source on the UK side said there were only really about five people who knew everything, only about a dozen negotiators thought to be in the team, and as the numbers go up, and the circle goes wider, the less information those people really hold.

Tuesday therefore - the day that Boris Johnson had wanted to be the election - has been hours of piecing together snippets of information from lots of different people with varying levels of knowledge to try to build a picture.

But through the day almost each conversation has brought a new contradiction - "they are definitely there - Varadkar and Johnson are in the same place".

The next chat, "there is no way, the chances of a deal happening are less than 1%".

On Monday night, Tory MPs full of bravado, "he's going to be a hero - I'll put money on it happening", another "it's clear there is going to be something".

Then a senior Labour figure reluctantly admitting "it sounds that way."

It IS very clear that what seemed pretty much impossible seven days ago could happen - there might be a deal ready for EU leaders to discuss and then perhaps sign up to on Thursday.

Those who are actually familiar with what's on the table keep using that phrase, "difficult but possible".

There have been at least 48 hours of genuine back and forth between the negotiating teams, proper consideration of whether the UK's reversioning of the Brexit deal can be wrangled to match up with the EU's priorities in a way that doesn't make it impossible for Boris Johnson to get a deal through Parliament.

At the UK end the prime minister is being careful to line up Brexiteers and the DUP, who are being briefed on the broad shape of the potential deal.

They aren't necessarily glowing about it, but nor are they condemning the possibility at this sensitive moment.

Some MPs are frankly desperate to vote for anything. Others are desperate to get to the point where they can try to push their own plan through.

In Parliament at least though there is a view that a moment of conclusion is on the way.

But for all that, it also remains difficult. DBP remember.

"Curb your enthusiasm," one government insider joked, if you were looking forward to it being done.

Negotiators will work into the night before the EU chief negotiator can brief ambassadors in Brussels on Wednesday afternoon.

Just because the politics have become much friendlier since Boris Johnson and Leo Varadkar's tramp round the country house gardens last week, it doesn't massage all the policy snags away.

But in 24 hours time we may finally know if this week at least, a deal now is so difficult that it proved impossible, or if it becomes, difficult but done.