Rumour has it that Jeremy Corbyn has changed his mind about Brexit – just in time for Kezia Dugdale's jungle outburst

In Ant and Dec’s jungle hideaway the other night, Kezia Dugdale uttered the most despairing sentence you may ever hear on the telly.

It wasn’t the most startling of the kind in I’m A Celebrity … Get Me Out of Here! history. That honour will forever belong to Johnny Rotten, whose reflex response to learning from Ant-or-Dec that the public had voted to keep him there was a trenchant: “You f****** c****”.

But Dugdale, recently leader of the Scottish Labour party, needed no more syllables than him to encapsulate a question of incalculable importance.

After pitching up late with the comedian Iain Lee, who beat her in a trial to become jungle Prime Minister, Dugdale was approached by that attention-seeking old rascal, Stanley Johnson. Unlike a certain son with more alarming prime ministerial ambitions than Lee, the erstwhile Tory MEP is a committed Europhile.

Stanley was looking forward, he said, with the relief of one whose hunger for celeb smalltalk was sated, to discussing Labour’s position on Brexit with Dugdale. “Maybe you can explain it to me,” murmured the absentee MSP for Lothian, so sotto voce you might have missed it.

Whatever one thinks about her quitting as leader in August to sign up for the show, you can’t blame her for that more muted expression of disloyalty to her party. Almost 18 months after the Brexit vote, we still await a clear Brexit policy from Jeremy Corbyn.

The word is that his position has shifted; that the passionate activist who campaigned for Remain with the lethargy of a secret Leave voter (though he denies it) has jettisoned his antipathy and come to see the point of EU membership.

Small wonder if so. When the facts change, good politicians change their minds, though there were no facts before the country voted to get us out there; just specious claims and outlandish counterclaims.

Now there are facts – the stagnation of the economy while Europe booms; those projections in the Budget that GDP will flatline for years to come; the hideous problem of the Irish border – and they are mortifyingly bleak.

If Corbyn thinks that an appalling mistake was made, and that it is essential to canvass the democratic will a second time in case others have also changed their minds on the strength of those facts, it would be awfully nice if he made it public.

Until now, the opacity has served him well. Whether through brilliant judgement or arch dithering (probably the latter), his failure to take a clear position worked wonders at the election. It avoided alienating both traditional Labour supporters who voted Leave, and young Remainers who worship him as the coolest grandad EVER.

Since then, his Brexit supremo Keir Starmer has played a blinder, quietly inching Labour towards what that canny observer Robert Peston identifies as one of the two destinations that logic demands: a sort of Norway option (membership of the single market and customs union continuing for a long while, if not indefinitely); or a second referendum in which Labour fights to reverse the result of the first.

Whether Peston is right, as I suspect, this chaotic stasis cannot last. The competing tensions pulling Theresa May in opposite directions – the jihadist fervour of her hard-Brexit suicide bombers, and the excruciating economic results if they are indulged – cannot be reconciled. They will tear her apart, as they will tear apart her successor and her party. The laws of political physics dictate this.

Whether Corbyn will benefit to the tune of a Pickfords van from Islington to Downing Street is anyone’s guess. Under a new leader wafting Lenor freshness, the Tories could revive.

But at this unusual moment in history, the occupancy of No 10 is for once on the political undercard. The headline act, which will define Britain for many generations, is whether this one-way trip to perdition can be cancelled.

With historic issues, there comes a time when even the most cynical politician has to stop playing politics. Corbyn is the least cynical of politicans, or has been. He has traded profitably on that image because for four decades he never wavered from his principles.

When no one but a few doughty souls in frowsty rooms above pubs would listen to him, he said exactly what he thought about the big issues of the day. Now everyone is listening intently, he is effectively silent on the biggest issue in peacetime history.

Like Theresa May, this cannot endure. If Corbyn has concluded that Brexit (even a soft one) will impoverish Britain, render it globally irrelevant, narrow the life chances not just of today’s children but of their future children, weaken its commitment to human rights, permanently damage the jobs market, threaten the long-term viability of the NHS and generally launch Britain on an irreversible downward spiral … if he genuinely thinks that, he needs to say so out loud.

It might be bad politics (though risking a reputation for honesty by fudging isn’t great politics). It would alienate some traditional voters. It could lengthen the odds against him becoming PM. But if Corbyn’s public life stands for one thing, it is the irreducible commitment to stating what he believes is true rather than what he calculates is to his advantage.

Considering what May’s Government has achieved in the last 17 months, the 16 months until the scheduled departure-date is the blink of an eye. Time is short. How much longer can Jeremy Corbyn permit a reference to Labour’s policy on Brexit to be answered with a wryly disdainful, “Maybe you can explain it me”?