The past few months have been characterised by weeks of high drama which, for all the excitement, have resolved nothing. But if Britain does end up leaving the EU without a deal, the moment when such an outcome became inevitable will be traced back to Tuesday’s telephone call between Boris Johnson and Angela Merkel. In that call, according to No. 10, the German Chancellor said that the EU will never sign any deal that could lead to Northern Ireland leaving its customs union. She said that its so-called backstop is not negotiable. If this is the case, the two sides will not agree.

Even if the Prime Minister were minded to leave Northern Ireland in the EU customs union for perpetuity, it would not pass through the House of Commons. No country can agree to have part of its sovereign territory in another customs union forever. The House of Commons could never agree to hand over control of territory in a treaty with no exit clause.

Parliament now stands ready to approve a different deal: one that agrees to a regulatory border between the UK and Northern Ireland. It is a concession many thought the DUP would never make. But if our maximal offer is less than the EU’s minimal demand, then we have reached a stalemate.

The Conservative party has collectively made an unforgivable mess of all this. It offered the country a referendum, but then elected Theresa May (with Philip Hammond as chancellor) to honour the results. They failed to do so. The idea of Boris Johnson agreeing a deal by 31 October was always a long shot, but he has carried on as if the sheer force of his optimism would make it work.

If open-ended membership of the customs union for Northern Ireland was always the EU’s red line, the past three months of negotiations have been a farce. Yet there is some indication — contained in the message sent by Downing Street this week to The Spectator’s political editor James Forsyth — that until early September Taoiseach Leo Varadkar was prepared to strike a compromise deal along the lines that the UK has proposed. Britain would, in effect, allow Northern Ireland to stay in the EU single market: following its rules on goods and services, but remaining outside the customs union.

However, that possibility was snuffed out by the Benn Act. Once Varadkar was convinced that Britain would be asking for a three-month extension he turned against a compromise deal. He would prefer to take a gamble on a UK general election, and see what it brings.

It is a dangerous game for the Taoiseach to play. Of the three options offered by each of the three main parties — a no-deal Brexit, another referendum or cancelling Brexit entirely — no deal is the most popular amongst a public who are now weary of this drama. Not all of them are persuaded by the idea that Britain, the world’s fifth-largest economy, is incapable of leaving the EU on its own terms. Too often, the EU looks at this as a mathematical calculation: surely Brits would not pull out if it was certain to involve economic pain? The answer came in the last referendum, and again at the Euro elections in May.

A no-deal Brexit would mark a failure for the Prime Minister. His assurance that there was a ‘million to one’ chance against that likelihood will not be forgotten. No less problematic for him will be a failure to leave the EU on 31 October. The inference of his promise, ‘do or die’, is that he should suffer political death for failing to achieve a positive outcome by that deadline. Aside from anything else, the Tennyson quote is ‘do and die’. The charge of the Light Brigade was not a victory. As the past few weeks have shown, optimism is not a strategy.

Yet there is little sign at present that Johnson will be punished electorally for these failures. On the contrary, his poll ratings appear to be on the rise — because, crucially, he has not broken any of his promises. If he were to go back on his word and keep the backstop, as the EU was belatedly proposing, then he would likely be defeated at the next election. The theme of his premiership is that the public has had enough of broken promises. Those who break theirs are never forgiven. Just ask Nick Clegg.

If we do end up with a general election, the Conservatives ought to be explicit: the EU can either accept the UK’s offer, or Britain will leave with no deal. It will be the last chance to focus minds in Brussels and end the game-playing. Disruptive though no deal would be, look beyond that and it is possible to see the advantages. It would offer an escape from the protectionism which has compromised EU trading relationships with the rest of the world. Britain can then start work on its important new role: being the EU’s greatest single ally. And building the wider, global relationships which lie on more distant horizons.

Brexit might force Britain into a general election, but the contest will offer a distinct choice: between a Conservative party led by a man whose instincts lie towards a free economy, and a Corbynite Labour party which would return Britain to failed socialist policies. Whether or not it can secure a deal with the EU, Boris Johnson’s government has everything to play for.