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It's not the official policy of the government yet, and the publication of more of the potentially gory details of leaving the EU without a deal is likely today.

But in government and EU circles it is more likely by the hour that there will not be an agreement at next week's EU council.

Despite the prime minister's assertion that his proposals are a "fair and reasonable compromise" - and signals to No 10 that some influential member states were willing to contemplate the concepts of the deal over the summer - in the words of one official, so far the EU had not shown a desire to "budge one centimetre".

In a call with the German leader Angela Merkel this morning, a No 10 source said "she made clear a deal is overwhelmingly unlikely", and even said the EU could veto whether Northern Ireland leaves the customs union, adding: "Talks in Brussels are close to breaking down, despite the fact the UK has moved a long way."

But there is no intention in Downing Street to move away from the broad concepts of what they are suggesting regarding either customs or the so-called principle of consent for gaining approval for the PM's plans from Northern Irish politicians.

So short of a political escape worthy of Houdini, this prime minister is moving towards making the case for leaving without a deal.

Now, as we've discussed many times before, Parliament's changed the law to make that as hard as possible. But No 10 still vows to do everything it can to press ahead - expecting further tangles in the courts, despite widespread scepticism that would have any effect.

And above all else, sources in government vow they would be as obstructive as possible to the EU, daring them perhaps to impose a delay on a reluctant and restive administration.

To their opponents, that might appear petulant and counter productive, but be in no doubt, if there is no deal this month, Boris Johnson's government would not suddenly play nice.

And in the likely event that there is an extension, for political reasons No 10 wants to give the impression it was forced into that position.

'Obstructive' strategy

Ministers hoped their proposals might get a fair hearing from the EU. But there is frustration that this just doesn't appear to have happened.

One senior source told me the talks are "meant to be a dialogue, not a question and answer session", suggesting that rather than getting down to business, the EU is simply tying up the UK's negotiators by making query after query after query.

Sources say the EU ought to listen "to the people who won the referendum, not the people who lost".

And there's a warning from this end that they will make a "historic miscalculation", if they expect saying no now will lead to calmer times ahead.

Back here, there's also an ongoing discussion over whether a future Conservative manifesto should include the outline of a potential deal with the EU or a straightforward plan to leave immediately without a deal.

I understand there has not been a decision on this yet.