All the hot takes and cold commentaries on Keir Starmer’s conference speech have – until now – failed to identify its most important line. Attacking the prime minister, Starmer delivered the following tricolon: “I don’t think Boris Johnson is a bad man. I think he is a trivial man. I think he’s a showman with nothing left to show. I think he’s a trickster who has performed his one trick.”

If you want to understand British politics today, everything you need to know is contained in that single moment.

People who live in or live off politics often talk about the importance of ‘a narrative’. Usually, they mean something linked to ‘framing’ (the context against which your claims, arguments and policies can, you hope, be found meaningful) or the need to present policies as part of a well-ordered whole. That’s all fine but it treats the idea of ‘narrative’ as metaphorical. That’s a mistake. Politics is not ‘like’ a story. It really is one. It appears in public culture as an actual drama, an epic tale of cosmic proportions; a battle or struggle for liberation, redemption and conquest, truth, salvation and revenge.

On the public stages of politics, we watch – cheer, boo and participate in – dramatic expressions and performances of the promises, contradictions and tragic flaws of our fragmenting culture. Political leaders, as well as their parties and policies, make sense to us because they evoke, as the sociologist Jeffrey Alexander puts it, “the already established skein of collective representations that compose culture… the universe of basic narratives and codes and the cookbook of rhetorical configurations from which every performance draws”.

Politicians today are a kind of celebrity. That is not only because we see them in newspapers, on television and online, as part of the same ‘feed’ as the one with all the stories about film, sport and music icons. It is because political actors – like movie stars – appear to us not as themselves but as embodiments of recognisable caricatures or types: the no-nonsense business leader; the tough guy who will keep us safe; the humble everyman-outsider; the corrupt king; the needy tyrant; the naïve fool surrounded by bad advisers.

As a critical analyst of the contemporary right-wing political drama, Starmer is absolutely correct. Boris Johnson is the trickster – or, rather, that is the part he plays in the drama he and his party have been contributing to and in which they have a starring role. Starmer is also right that the trickster is not exactly bad. He is an agent of chaos. He is a rule-breaker who mocks authority.

Unfortunately for Labour that makes the trickster often quite appealing. Bugs Bunny, Bart Simpson, Loki: the trickster is charming and entertaining. And because he breaches convention (showing it up as mere convention) he feels subversive and exciting and as if he is revealing something to us, showing us the trick authority has played on us.

That’s only half the story, however. If Johnson is the trickster, what role is Starmer playing?

The answer is obvious, often noted and completely under-appreciated. He is Sir Keir. He is a knight, bearing the name of his party’s founder. Few things are as mythical as the return of a heroic founder, and the conference speech gave Starmer the chance to play the role of the One who will bring the party back to its senses, back to reality and back to life.

He performed the role of a pure or natural spirit, born into the movement, who just knows in his heart what’s right. He didn’t learn it “in some political seminar”, he said. He is “not a career politician”, he “came to politics late in life” and sits above the “point-scoring”. And lo, did he endure the scorns and heckles of the jealous Pharisees and sloganeering sophists.

But more than that, countering Johnson’s chaotic-neutral pagan spirit, Starmer took up the role of lawful-good, Arthurian knight. As he explained in the speech, Starmer comes from humble beginnings. He is the son of a practical man, grounded in his vocation, and imbued with an appreciation of real work.

Starmer’s virtue was demonstrated by his story: how he changed his stars, rose up the ranks and was ultimately entrusted (as director of public prosecutions) with the duty of dispensing justice and issuing punishment wisely and fairly. He did so understanding “that there’s one law and it applies to everyone”. And he abided by the codes of old English chivalry: humble, he befriended and wept alongside victims of cruelty and injustice; brave, he was sure to avenge them.

Yet, as the conclusion of his speech told us, he now fights not with a sword but with a loom. He is a weaver, stitching the fabric of the nation back together.

To be clear, I do not think that Starmer and his advisers made anything up. No more than Johnson do they knowingly cultivate such dramatisation. Myths and legends are one of the means through which we perceive the world, part of that ‘skein’ of representations, codes and narratives.

To understand Starmer’s performance you don’t have to remember – though some in the conference hall probably do – the 20th-century children’s hymn, which instructed that, “When a knight won his spurs, in the stories of old/He was gentle and brave, he was gallant and bold,” and which explained how, in these days when “back into storyland giants have fled”, we should still go into battle “’Gainst the dragons of anger, the ogres of greed”.

Labour people love that sort of mythology. It runs deep through the traditions of English Christianity and socialism and has been performed by several lords of the realm, from across the party’s factions. The Labour Party wants, on the one hand, to embody and represent the interests and demands of a particular part of society. But, on the other, it wants to stand for the values of society itself, and to embody universal ethical principles of order and justice. It has struggled with that tension but usually resolves it in favour of the latter, despite, as the song says, the flinching of cowards and the sneering of traitors.

A problem for Labour is that for so long our culture has been teaching itself to embrace the trickster. After all, as well as the entertainer and online troll, the trickster is the counter-cultural rebel, the heroic entrepreneur, the visionary disruptor. Living by the motto ‘move fast and break things’, tricksters are creatures of self-invention and reinvention and very much the spirit of the times.

Against that background trickster politicians – Farage, Trump, Johnson – have captured the mood of what Jonathan Hopkin has termed ‘anti-system politics’, hostility to a status quo that is tired, broken and often harmful, fusing it with the idea that liberty and individuality are synonyms for wilfulness. In the pagan world of the trickster there are many deities and his political avatars increase in number all the time, promising, “Follow me and I will make you a god of your own land.”

In contrast, the Arthurians offer us a series of rather unheroic roles. We can be one of the knight’s loyal retainers. We can be one of the wicked people who denies his virtue. Or we can be one of the passive, suffering souls waiting to be saved by the good guys.

A problem for Labour – for the Left and liberalism – has always been that people who are confident their actions accord with the rules of morality can easily seem intolerantly pious. The knight without dragons, without enemies to vanquish, becomes a technocrat, managing and applying the chivalric code to the rest of us, generously promising to make us as virtuous and as noble as they, asking only that we be grateful. That gives Loki his chance.

Affirming Johnson’s trickster persona was a mistake. It gives Conservatives an opportunity to yet again portray Labour and the Left as people who want to tell you how to live your life (and tell you off for not doing so properly). The rhetorical dramatic challenge for Labour is to reveal Johnson as a clown rather than a trickster; an incompetent, instead of cunning, creator of chaos. That is, clearly, a script to which Johnson is very able to contribute. In that, luck – the most powerful deity in politics – may yet bless Labour. But that will not end the narrative.

British politics right now is not simply a mythical clash. Johnson’s Loki and Starmer’s Galahad are single players in a much larger clash of mythical universes. The stages are getting crowded and sometimes it is hard to tell who is a performer and who is in the audience. And we are not yet anywhere near the end of the first act.