Last Tuesday, on one of the thousands of occasions I glanced needlessly at my phone, it made me notice a news story. Vince Cable, it appeared, had described the hardcore Leavers’ delight in Brexit as an “erotic spasm”.

I liked that. It’s a nicely rude way of describing their irrational excitement at continental division and national isolation, and their inappropriately visceral feelings about the technical details of international trade deals. The whole country is going through a disaster, it is saying, just so a few extremists get to judder with sexual delight.

And it’s doubly potent because of who the leading Brexiters are. Jacob Rees-Mogg, Boris Johnson, Michael Gove and Nigel Farage are people who it is particularly grotesque to imagine having an erotic spasm. In my view, anyway. Yet that grotesqueness has a grim fascination – I can’t help thinking about it, about each of them wriggling around, all spermy and thrilled.

Of course that’s not their fault. The fact that they’re not conventionally attractive, and so their credibility is unlikely to be enhanced by lots of people imagining them in sexual contexts, is an unfair reason to dismiss their views. And I say that as a thoroughgoing non-oil painting myself. But that’s one of the many things about the world that isn’t fair, so I have to accept that what I say here is just going to seem less persuasive when I admit that I’m masturbating as I type it.

Cable just ploughs on as if 'exotic spresm' means something, or as if the right noise could be dubbed on to the speech

Then it turned out that Vince Cable hadn’t said it after all. The current irritating system whereby the texts of politicians’ speeches are circulated to the media before they’ve been delivered rather relies on our elected representatives being able to spit out the words as planned – which is easier said than done. Or rather said. Certainly easier said than “erotic spasm”.

I’m sure Cable knew it was a good line – he paused slightly before trying to pronounce it, indulging no doubt in an instant of self-satisfaction. “This’ll get ’em!” he probably thought. I know from my own experience that there’s nothing like feeling sure the next line is a zinger to make your teeth, tongue and saliva try to join in with saying it.

So he said “exotic spresm” instead. It’s very funny. I recommend watching it. Not the whole speech – that’s interminable – but that section. I knew in advance both that he was supposed to say “erotic spasm” and that he’d actually said “exotic spresm”, and yet somehow that made it even funnier.

He’s standing in a huge room full of people most of whom presumably know he’s about to try to say “erotic spasm” – I mean, I knew in advance and they’re Lib Dem members who are attending the Lib Dem conference, so they’re bound to. They’re all ready, keyed up to laugh approvingly as soon as he says “erotic spasm” and off he goes: “Years of economic pain justified by…” little pause – stand by, conference… “the exotic spresm of leaving the European Union.”

There is a quality to the silence following the remark that is almost magical. It’s pure distilled human puzzlement. Hundreds of people simultaneously wondering if they’ve lost it, if the part of their brain that decodes language has suddenly failed. It’s a puzzlement exacerbated by the fact that Cable just ploughs on as if “exotic spresm” means something, or as if the right noise could be dubbed on to the speech in post-production. He doesn’t otherwise fluff or stumble, and so it’s not even clear that he’s aware he’s screwed up.

Anyway, it’s all good fun, largely because the Lib Dems seem so irrelevant these days. They went back on their tuition fees pledge and it virtually destroyed them as a political movement. Fair enough: tuition fees are the big issue of our time. That’s what all the historians will focus on when they write about this era: the great tuition fees conundrum. How Britain struggled with its huge and painful divisions caused by the towering question of tuition fees.

To be honest, I was pretty pissed off with them when they did that. I don’t think they got nearly enough out of the Tories for propping up Cameron’s government – basically just a referendum on a half-arsed form of electoral reform when they might have got a commitment to proper proportional representation. Now that would have been worth betraying the students for. But, as it was, they fell for Cameron’s rhetoric about national crisis and used all their power to spare his electoral embarrassment, so that, now the country really is in crisis, they haven’t got any left.

That’s a much less amusing cock-up than Vince Cable’s speech because the consequences are proving disastrous. The Lib Dems are the only political party wholeheartedly representing the 48% of voters who opposed Brexit, yet the chances of them securing those people’s support in a general election are vanishingly small.

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To my mind, the Lib Dems are right about so much and yet it does them no good. They consistently opposed the Iraq war, for example, which is now an extremely mainstream view. Obviously the Labour party is very down on the Iraq war these days but, crucially, that wasn’t the case when it was actually happening. At that point, both Labour and the Tories were all for it.

The Lib Dems are also the only political group that’s consistently advocated proportional representation, and their failure to gain traction there may be the biggest disaster of the lot. It’s because of the first-past-the-post voting system that neither Labour nor the Conservative party can split without facing electoral annihilation. So Cameron called the Brexit referendum to keep the Tories together, and the majority of Labour MPs remain part of an organisation they believe to be ineptly or even malevolently led.

The energy required to keep the Conservative and Labour parties ostensibly united is tearing Britain and Europe apart. Meanwhile the hapless and laughable irrelevance of the only political movement properly addressing the country’s biggest problems is a fascinating manifestation of our looming national disaster.

We get meaningless and useless nonsense from all of our political leaders at the moment. But, when Vince Cable does it, at least it’s just a slip of the tongue.