Wanted: a siren and flashing blue light for the prime minister. We know from her conference speech that she sometimes goes unprepared. Today the paraphernalia of the emergency services would come in handy.

Theresa May is now off to Brussels for dinner with Jean-Claude Juncker, and the hope is that this time he will give her the time of day, for no one could bear another of those European events where our prime minister loiters alone while the other leaders glad-hand – Theresa no mates. The hope is that she’ll fare better than the last time she dined privately with Juncker. Soon afterwards – to her complete detriment – his people leaked the whole thing.

Her officials say the meeting has been long planned. But that’s strange because when the other day Juncker detailed his forthcoming engagements, a tete a tete with May wasn’t mentioned. Three possibilities present themselves. Either he needs a new diary secretary, or the meeting comes so low on his list of priorities that it didn’t merit listing. And then there is the most likely explanation given how the Brexit process has gone so far: that Theresa’s people are telling porkies.

She can – she should – say that the talks are being held on Earth rather than in Narnia

So off she goes, the Red Adair of Brexit, hoping, we must hope, that she can avert the disaster so far conjured up by Davis, Fox and Johnson, the Marx brothers of her government. If that’s true, we must wish her well.

Because the time has surely come for the nearest thing the government has to a grownup to take things in hand. Last week, more than any other since the vote itself, catastrophe became a real possibility as the Brexiters and their water carriers in the press launched their grooming process to make crashing out of the EU, with no deal and no safety net of any sort, the preferred option.

We know that for most, this is a response to the fact that talks aren’t going well and that – as the UK was warned would be the case – EU leaders refuse to see themselves as supplicants. They may prefer a deal with us over no deal, but not at any price. They have their own priorities, not least the continuation of the EU itself, and their own domestic politics. If May, somewhere between the main course and the port, communicates a willingness to have a proper conversation rather than the infantile game of chicken being played by the Marx brothers, her trip will have been worthwhile.

She will, no doubt, stick to the line that the people have spoken, that we are leaving and that’s an end to it, but she can – she should – say that the talks are being held on Earth rather than in Narnia, that everything else not mandated by the vote is flexible. She may feel the threat of hard Brexit will concentrate minds on the continent, and in the manner of sympathy it may do so. But that’s a perilous strategy. All she would be saying is that Britain will detonate itself and Europe will be covered in splatter. As it would. But Europe would soon scrape it off.

May and Davis to travel to Brussels for urgent Brexit talks Read more

This is a moment. If hard Brexit – deified again this morning on the Today programme by John Redwood (the Marx brother no one knew or cared about) – solidifies as the default position, all is lost. We will have been bullied, nagged, bamboozled into a position that some desired but no one can claim to have voted for in the idiotic yes/no ballot. It is a moment for all who view a cliff edge as sane folk normally do to throw their weight behind a sensible Brexit.

The Brexit-at-any-cost contingent know that too. That’s why Redwood today characterised any drift as a soft Brexit, as a drift towards Labour that no Conservative could countenance.

Theresa May has her part to play, but so too does parliament. The majority of the Commons know what a sensible Brexit looks like. Now is the time to fight for it, accepting all the while that the whole thing might yet fall apart, making a rethink a necessity. The siren and the blue light should be flashing there too.

• Hugh Muir is a Guardian columnist