It is incontestable that the Brexiteers won the referendum, albeit by a small margin. A win is a win. But that does not mean it is the last word on the subject. One of the advantages of our flexible constitution is that we always have room for manoeuvre; we always find a way of muddling through. And time has a way of changing the way things look: options that look impossible now may well seem possible by the autumn.

You just have to look at the glum faces of the Brexit leaders (with the exception of Nigel Farage) to see they realise they have brought about the biggest self-inflicted wound in our history. They show every sign of suffering from a bad case of buyer’s remorse, with no idea what to do next. Drifting away from the undertakings they made during the campaign, they appear to be making it up as they go along. Certainly they can’t offer us a way out of the crisis they have created.

In the face of the mayhem in the markets and over sterling, with economic consequences that are likely to last for years rather than days, the only sensible thing to do is to pause and think. We don’t have to trigger article 50, which commences unstoppable negotiations on exit, and no one in Europe can make us do so. European politicians are urging us to hurry up and end the uncertainty. But beginning the negotiations is going to open up at least four to five years of uncertainty, not end it.

In any case, we have to wait for the Tories to choose a new leader in the autumn. And whatever Boris Johnson says, that leader will have to call a general election to secure a mandate for negotiations with Brussels; it is no good the Conservatives trying to use their majority in parliament to avoid such an election. If they do so, what they negotiate will have no legitimacy.

The referendum was a vote against something but it wasn’t a vote for anything. It tells us nothing about the new relationship people want with Europe. The Brexiteers never told us what they collectively stood for. Some were for becoming Norway, still inside the single market; others, like Johnson, for becoming Canada, with a free trade agreement with the EU; and still others, like Nigel Lawson, were for opting out of all agreements and relying just on World Trade Organisation rules. Now they realise that services, about 80% of our economy, would be largely excluded from any Canada-style deal, they are drifting towards the Norwegian option.

Facebook Twitter Pinterest Jeremy Corbyn ‘patently cannot’ win a general election. Photograph: Lauren Hurley/PA

But that would require us to continue to accept free movement of people, to make a payment to the EU roughly equivalent to the net amount we contribute at the moment, and to implement the rules and regulations of the union without having any say in the making of those rules. Such an option will bring down on them the wrath of their erstwhile supporters. Johnson’s line during the campaign that he was in favour of having our cake and eating it too doesn’t look so funny now.

The choice between a future as Norway or Canada is crucial, not only for economic reasons important as they are, but also for constitutional reasons that people seem not to have fully grasped yet. If we opt to leave the single market and have our own trade and immigration policies, there is every prospect of the United Kingdom breaking up.

It is clear there will be a referendum in Scotland if we leave the EU, and fairly clear that those seeking independence will both win that referendum and take Scotland back into the EU. We will then have no choice but to have a hard border between Scotland and England: you can’t have two different customs policies without customs posts and customs checks.

And if England stops allowing free movement of EU nationals, as the Brexiteers have promised, and Scotland continues it as part of the single market, we will also need passport checks along the border. The position facing Northern Ireland will be even more dire. They will have hard borders with both Scotland and the Republic of Ireland, not to mention reopening the basis of the Northern Ireland peace process, which was an open border between north and south. Paradoxically it is the Little Englanders who will have brought about the end of the United Kingdom.

Given Johnson’s apparent flexibility, all we need now is for him to drift back to his original position before he broke his personal assurance to the PM and became leader of the out campaign. Then he said the best option for Britain was to vote to leave the EU, to have a new negotiation to get a better deal than Cameron, and put that to a further referendum. Of course, the Europeans are objecting strongly to that idea at the moment, but it may look better when they’ve time to consider the alternative.

There are plenty of precedents for having two referendums, one after the other, on Europe. The Irish have done so twice in recent years. The first time on the Nice treaty in 2001 and then on the Lisbon treaty in 2008/9. In each case the Irish people rejected the treaty the first time round, only – after some changes – to accept it by a large majority the second time round.

If the Tories are to be led by an anti-European, and Iain Duncan Smith claims it is their constitutional right after the referendum, then someone has to speak for the 48% of the country who want to remain in the EU. After his dismal performance in the referendum, allegedly going as far as trying to sabotage the campaign, Jeremy Corbyn clearly can’t be that person.

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The Labour party is now in the process of choosing a new leader who represents the pro-Europe mainstream of the party; a leader who can win a probable election in the autumn, which Corbyn patently cannot. There will be warnings that a pro-European stance would risk losing working-class voters to Ukip. But we will lose them anyway, unless we run on an anti-Europe manifesto, and there are compensations such as making progress in Scotland in a way an anti-European could not.

The new leader needs to run in the general election on an explicit promise to negotiate with our partners to salvage our position in Europe, rather than to leave it. In our system, as in most others, a general election trumps a referendum. If the new Labour leader wins, he or she will have a mandate from the British people to negotiate a new, positive position for the country inside the EU and put that to a second referendum.

We still have time to save ourselves from the national catastrophe brought on us by David Cameron’s ill-judged decision to hold a mid-term referendum on Europe. There is a way out, but it requires political leaders with courage to make it possible.