Oil paintings are probably the only evidence not introduced by party spin doctors as they tried to claim victory for their leaders – even the ones who weren’t there – after last night’s BBC televised debate of the 2015 general election. Yet looking at the debate’s closing image of Ed Miliband shaking hands with Nicola Sturgeon as Nigel Farage stands isolated to our far right, I cannot help thinking of some grand narrative painting of a moment in history.

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This handshake has the formal, momentous quality of, say, the meeting of Dutch and Spanish generals in Velazquez’s painting The Surrender of Breda. Sturgeon seems almost to bow, as the Spanish leader does in that masterpiece of history painting. All it lacks is someone looking out of the picture, catching our eye, commenting silently on the falseness of the moment, the complexities behind a simple image of friendship and possible alliance.

Perhaps some will see that ironic commentator as Farage, who voiced his discontent with the event itself and the composition of its audience, and claimed to be uniquely addessing the real audience watching at home.

Yet this painting – sorry, photograph – has other echoes that are even more suggestive. Sturgeon approaches Ed not alone but as one of a triumvirate of leftwing women (to ignore the gender of that Latin word for a political union of three leaders). They move towards him together, and the picture captures a rhythmic, dynamic strength reminiscent of one of the most radical of all European paintings.

They are interleaved like the ancient Romans who swear to the common cause in David’s painting The Oath of the Horatii. David took this way of showing three figures in a layered congregation from ancient Greek art: it is a very classical moment. But it is revolutionary, too. The Oath of the Horatii, painted in the 1780s, expresses the idealism and intensity that led to the French Revolution. Is Britain, too, on the brink of its own kind of revolution?

This is the election of a new British left – the anti austerity parties are making the running

This meeting, with the weight of a painted history, captures something truly new in our politics – the moment England had to accept the equal voices of Scotland and Wales at the heart of a general election, and the moment the Labour leader had to prepare to be the staid voice of caution in an alliance, or rainbow or grumpy getting-along of leftwing forces, in which Scottish radicalism sets the pace.

This is the election of a new British left – the anti-austerity parties are making the running. Or rather, the SNP is. There really is a radical mood in these countries, and forces have woken up that traditional Westminster or the mainstream media or perhaps we ourselves can’t comprehend. We’re not necessarily who we thought we were.

I have a strange confession. I like Leanne Wood. She got just 2% in this week’s instant rating of the speakers, a slight improvement on the first debate, but I find her eloquent. Why? Well it could be that I am Welsh. I am a Labour voter but I certainly did not share the scepticism she seems to incur with non-Welsh people. And that’s significant. The British Isles are not one monolithic thing with its head in London and its heart in the southern English shires. We all have different loyalties and priorities that may surprise us – who knew I had a nationalist fibre in my being? – and these feelings of revolt are brought to the surface by the repellent spectacle of five more years of Tory rule.

I expected to be bored, alienated and repelled by this election. Instead, it is the most exciting since 1997. Why is that? Something new is happening. This image captures what it is. Here is the reality of Britain now: a new union, a new shape of things to come, as strange as a mythological gathering chanced on in a glade. Forget the political calculations. What is democracy telling us? That Britain, a diverse and complex constellation of countries, is headed, in its nuanced way, leftward.

No wonder Farage looks lost and disconsolate, far off in the isles of the troglodytes. Ukip looks left behind by history here. Farage is far, far from the herd. He’s like the burning villages in the background of Velazquez’s Surrender of Breda – the inconvenience no one wants to look at.

The sense that something strange and new is happening is even more apparent in the debate’s other defining image, of Miliband looking on as the women embrace one another.

It’s probably a wildly inappropriate pre-feminist art historical reference to say that Nicola Sturgeon, Leanne Wood and Natalie Bennett looked like the Three Graces in their group hug at the end of the debate.

Facebook Twitter Pinterest ‘The Three Graces, an artistic masterpiece that symbolises reason and peace and is shared between Scotland and England, is a fitting image for this dazzling moment in British politics.’ Photograph: Handout/Getty Images

In art, these goddesses of the civilised virtues are traditionally represented in a three-way group hug not so different from the one that united the critics of austerity in this image of Britain’s radical forces getting together in mutual support.

The Graces gather arms intertwined in Botticelli’s painting Primavera and embrace, even more reminiscently of Sturgeon’s gang, in Canova’s marble statue of the Three Graces, carved as the Napoloeonic wars ended.

As it happens, Canova’s Three Graces is today jointly owned by the National Galleries of Scotland and London’s V&A, so perhaps it is, after all, a curiously fitting analogy. Could Nicola Sturgeon even be unconsciously channelling it? The Three Graces, an artistic masterpiece that symbolises reason and peace and is shared between Scotland and England, is a fitting image for this dazzling moment in British politics.

If this was a gaggle of anti-austerity goddesses, what did that make Ed Miliband? Isolated from the group huddle and looking on wistfully, he too resembled a figure from Greek myth – perhaps one of those forlorn men who chances on powerful goddesses at woodland pools and gets turned into a stag. Miliband for a moment resembled the doomed Actaeon in Titian’s painting Diana and Actaeon, which is also, as it happens, shared between Edinburgh and London. Presumably that made Sturgeon this election’s incarnation of the all-powerful divinity Diana the huntress.

All these mythological echoes cast a harsher light on Farage, too, in that picture of him standing far off from the handshaking leftists.

Far away, utterly excluded from the realms of the beautiful and wise, he resembled the cyclops Polyphemus, glaring at the world from his one eye. Farage’s unravelling as a national figure is the delight of this election. He really did adopt the role of the one-eyed mythic monster the Cyclops, howling contempt for the “biased” studio audience as he leadenly tried to fit every issue into his tunnel vison of a Britain all of whose problems can be blamed on immigrants. In this debate, Farage was a lonely monster retreating to its cave. Let’s hope he stays there.