We should know on Wednesday night whether Boris Johnson has his Brexit deal proper, or whether he has an outline deal that will require a few more weeks of technical talks, or whether the gap is unbridgeable.
Why? Because Donald Tusk has made it clear there will be no serious negotiations at the EU council itself on Thursday and Friday, just a rubber stamping exercise.
But Johnson knows that if he wants an actual deal this week, he’ll have to sign up to something very like a Northern Ireland-only backstop, which would represent a massive eating of humble pie – not cake – for him.
It would also be hard to sell to the DUP, who were in to see him on Monday night and 'don’t think' they are about to be sold out.
But Brussels believes there is a way to make Northern Ireland-only backstop palatable to a DUP that wants a route to a deal.
For Johnson there is a question about which is the bigger humiliation – either belatedly signing up for a backstop-bridge to his preferred arrangements for keeping open the border on the island of Ireland or a Brexit delay that might not deliver the deal he wants and would most definitely breach his only red line anyone remembers (namely do-or-die Brexit on 31 October).
For the first time since becoming prime minister, he faces a choice that will see him embarrassed – or worse – whatever he does.
Robert Peston is ITV's Political Editor. This article originally appeared on his ITV news blog.