What will happen at 'moment of truth' Brexit summit? Who knows!

It's honestly very hard to know how the next two days will play out.

In a sense we are precisely where most of us expected we would be at this end stage of the Brexit saga.

The two sides take it to the wire; the negotiators have done as much as they can and it's now up the politicians - the EU leaders - to break the ever-predictable impasse.

The thing is, it's genuinely very difficult to see how the last remaining circle - the Irish question - can be squared.

In a nutshell, it's this (bear with me here):

:: Neither side wants a hard border on the island of Ireland largely, but not only, because of what it could mean for the peace process.

:: So when Brexit is a distant memory and the UK is firmly (happily?) out of the European Union, the border between Northern Ireland and the Republic of Ireland must look precisely as it does now - invisible.

:: The UK has committed to leaving the EU single market and customs union - because only by doing so can the UK sign its own trade deals globally.

:: That decision means that a hard border on the island of Ireland is unavoidable, unless...

:: The UK says it can avoid a hard border because it will, eventually, strike a rich free-trade agreement with the EU.

:: The EU says this may be possible but there is no guarantee, especially not within the two-year implementation period from March 2019.

:: Because there is no guarantee of a deal deep enough to prevent a hard border, there must be a "legally binding backstop" position to prevent one.

:: So either, says the EU, the backstop involves Northern Ireland remaining in the customs union or, they conceded last week, the whole of the UK can remain in the customs union.

:: The UK insists that any backstop must be UK-wide (so that Northern Ireland isn't split from the rest of the UK) and that it must be time-limited.

:: There must, says the UK, be an end date to the backstop so that the UK doesn't end up remaining tied to the EU forever.

:: The EU says it's not a backstop if it has a time limit. They argue that to give the backstop an end date means they are committing now to a free-trade arrangement that is as yet not negotiated and may not be deliverable.

:: There's even been talk of a backstop to the backstop... but let's not go there now.

:: This is their conundrum.

They are deadlocked over a hypothetical scenario and the irony is that if the negotiations collapse as a result of this hypothetical and there is no exit deal then there will, by definition, be a hard border in Ireland.

The EU side says it is up to the UK to come to the table with proposals which will solve the conundrum.

Essentially, an EU source told me, the UK has to work out what sort of future trading relationship it wants with the EU.

:: EU leaders put pressure on May ahead of summit

The suggestions it has come up with hitherto (the Chequers proposal) won't fly with the EU because they amount to cherry picking and undermining the union.

So, back to what will happen this week: Theresa May will address her fellow leaders before the pre-summit dinner.

The president of the European Council has said he hopes Mrs May "will present something creative enough to solve this impasse".

The problem is that the closer she moves to presenting something that will solve the impasse the less acceptable it will probably be to MPs back home.

So if she gets to a position in Brussels where a deal is on the table - she then has to sell that deal back home.

One option that's being tossed around as a possible solution is an extension of the two-year transition/implementation period.

The EU hasn't been against extending the transition before - it's to their benefit, not least because the UK would have to pay into the next multi-annual budget.

But many in Britain would argue it is not at all in the UK's interest because it would mean remaining bound to a club but with no seat at the table and no real ability to influence decisions.

There is some encouraging news: the timeline has once again magically become more flexible.

Just a few weeks ago, this week's summit was described as the "moment of truth" - the make or break summit.

Now that it's clear there's still a problem, more time has been found.

"Whether they are concluded sooner or later is not material. We have to get the right deal that works for all," the Austrian chancellor said this week.

Prior to this latest bust up, the plan was to have an emergency November summit to finalise the deal that was to be struck deal this week.

It's possible, probable even, that the November summit won't happen now. But that doesn't mean all hope of a deal is lost.

On the contrary, it means that they think it's worth giving more time for further negotiations and, so hopes the EU side, time for a consolidation of views in Westminster.

All eyes could now be on a December summit deal.