Boris Johnson’s Brexit offer to the EU is not dead on arrival – but it may well be dead within the next 48 hours.

And that could become clear as Michel Barnier, the EU’s chief negotiator, briefs EU ambassadors and MEPs about what he sees as the deficiencies of the proposals.

The biggest hole, as you would expect, is that EU government heads are being asked to take on trust that all the legal and technical preparations necessary for checks on goods and food flowing from Great Britain to Northern Ireland, and all the legal and technical preparations for customs checks away from the Northern Ireland border, will be completed by the end of 2021 at the very last.

2021 is the last date for the whole UK to exit from the EU’s single market and customs union (the preferred date for this full Brexit for Johnson is the end of 2020).

The whole point of that notorious backstop that Brexiters hate and Johnson wants to dump, is that EU leaders don’t believe Johnson’s Northern Ireland customs and market preparations can be completed in time.

And if they didn’t trust the more consensual government of Theresa May, why would they trust the spikier one of Boris Johnson?

Also, many EU leaders hate the idea that six months before the new Ireland food and goods single market would come into force, it could be scrapped by the Northern Ireland Assembly and Northern Ireland Executive.

The market would be at permanent risk of being closed down every four years after that, because Johnson is insisting that Stormont would have to renew consent for the market on that rolling basis.

This provision would provide a permanent risk to the EU’s stipulation that the all-Ireland economy must be preserved.

Finally, there is simply deep scepticism in Brussels that the new customs arrangements can be put in place without involving the construction of new infrastructure – against the spirit of the Good Friday Agreement – and EU leaders fear these arrangements would in practice compromise the integrity of the EU single market.

So for all those reasons, my strong sense is that Paris, Berlin and Dublin will not agree Johnson’s plan.

And we may know that very soon indeed.

At which point all attention will switch to whether Parliament can in practice block the PM’s plan to take the UK out of the EU without a deal.

Robert Peston is ITV’s Political Editor. This article originally appeared on his ITV news blog