As William Hague writes in today’s Telegraph, the Prime Minister’s best shot at getting her deal through the Commons relies on encouraging a ‘balance of terror’ among her two disparate groups of opponents: ‘She needs hardline Brexiteers to worry that if they don’t vote with her, Brexit won’t happen at all, and some ardent Remainers to think that unless they support her, Britain will “crash out” of the EU without a deal.’

We’ve already documented one evident problem with this strategy – namely that because both persuasion campaigns are happening in public, each side can hear the messages intended for the other. That helps to explain why it’s yet to work on either group.

Downing Street evidently isn’t giving up, though. Today it is the Brexiteers’ turn to be targeted with a mystery leak which coincidentally communicates exactly the “No Brexit” warning that the Prime Minister would like – that British officials are supposedly ‘putting out feelers’ in Brussels about the possibility of extending Article 50.

The story illustrates exactly the difficulties Downing Street is facing. Such a prospect will indeed concern some Leavers. But it will also infuriate others, while simultaneously undermining the argument to Remainers that the alternative to the Prime Minister’s deal is a No Deal exit from the EU. It’s far from clear that there’s any net gain from this approach at all – at best it might produce what Hague terms an ‘equilibrium of complacency’.

Interestingly, it’s not completely, or at least solely, a comms tactic – there is also some debate on this topic inside Government. I’m told that some of those – including David Lidington – who favour an exhaustive series of ‘indicative votes’, the idea by which Parliament would get to give its verdict on every possible Brexit outcome, see an Article 50 extension as the only way to address the rather large problem that there isn’t time to carry out their plan.

Number 10 is resisting this suggestion. In part that is because the Prime Minister’s team are not keen on the ‘indicative vote’ idea, given that they have a specific proposal they wish to sell. They take the view that such votes would just allow the Commons to indulge its varied and conflicting dream outcomes, when actually MPs ought to focus more on what is really on offer. But the second reason is that a delay to Article 50 would itself be severely damaging. First it would deal a blow to the Prime Minister’s plan, which would lose the threat of a hard deadline which is one of its few selling points, and then to the Government itself, which would find every troublesome group, from Stop Brexit Remainers to Start The Negotiation Again Leavers, emboldened by the message that it is possible to create extra time for any approach you might wish, contrary to the current assurance that the clock is ticking down inexorably.

There’s also the question of basic practicality. Even if the UK did request an extension to Article 50, why would the EU grant it? There are only a few possible reasons Westminster could give to Brussels to justify the request. If it was to give more time for No Deal preparations, it’s hard to see why the EU would do something it would see as helping to undermine its own internal messages about the dangers of trying to leave. The offer which might tempt the EU – that an extension would provide room to reverse Brexit, perhaps through a second referendum or new election – would hardly be consistent with the promises of the Government or conducive to its survival in office.

In short, even if an extension were possible theoretically, it might not be achievable practically. If it proved to be achievable practically, the price would be outrageously high and politically unacceptable to many Leavers. If, somehow, that price was paid, any and all of those who had thought an extension desirable would find their own plan for how to use the time would be consumed either by the EU’s conditions for providing it, or by the free-for-all reopening of the whole debate from square one which the decision would spark. It has reportedly become common for ministers to dismiss Brexit plans they deem fantastical as ‘unicorns’ – if so, this one has bells on it.