Hunter, a former member of Theatre de Complicite and a leading exponent of physical theatre, is directing Aristophanes’ comedy The Birds as part of the National’s Transformation season.

Birds, flight, trapezes — that might seem an obvious sequence of thought. But it was only after Matt Chamberlain, the director of Mamaloucos Circus, asked her to consider a circus-theatre piece that Hunter thought The Birds could be what they were looking for.

The play, first performed in Athens in 414BC, displays Aristophanes’s style of mixing fantastic comedy, the preoccupations of “ordinary” people — as opposed to the usual mythical gods and heroes — and political satire.

He has two characters, Peithetairos and Euelpides, who flee the bureaucracy of the city and set up a Utopia with birds as its subjects. But it is not long before the corrupting influence of power begins to assert itself and the idea of democracy is brought under scrutiny.

The Birds was written two years after the Athenian army had massacred the inhabitants of the island of Melos, during the Sicilian expedition against Sparta’s allies. It was an atrocity which caused shock-waves in Athens. But, says Hunter, “Aristophanes is not didactic in the way that Brecht is. He puts up warning signals about power-seeking. The proposition of the play is that we have to carry on dreaming of a Utopia, then look at how to achieve it. He is not saying that it is ridiculous to dream, but that we must analyse our intentions. He wrote the play when Athens was suffering from vanity as the birthplace of democracy.”

Hunter sees a parallel here in the West’s certainty of its ownership of democracy on the world stage now. She also finds the protective wall that Peithetairos builds for the new kingdom has obvious resonances for a country at a loss in coping with asylum-seekers.

Throughout the centuries, directors have found a contemporary resonance in Aristophanes’ works. Goethe used a 1780 production of The Birds to satirise his Weimar contemporaries and the public’s fickle tastes. Recently the Italian Prime Minister Silvio Berlusconi was involved in a censorship row over a staging of The Frogs that dared to satirise him.

Hunter, however, says that contemporary parallels aren’t overplayed in her production. It uses a new translation by the Irish poet Sean O’Brien that adopts a streetwise style. Peithetairos and Euelpides here become Pez and Eck, while the premise of the first half is that “all the world’s a circus ring”.

Pez and Eck are played by Marcello Magni and another acclaimed physical theatre performer, Hayley Carmichael. They wear the baggy trousers, if not the full make-up, of clowns.

As Pez and Eck address the king-turned-bird Hoopoe (Josette Bushell-Mingo, one of the original London leads in The Lion King) and are attacked by the birds, circus convention runs parallel with the drama: different bird characters use trampolines, trapezes, strops (looped straps suspended from the ceiling) and ropes to menace the newcomers.

The trapeze alone would, says Hunter, be a cliché. When Pez persuades the birds that they can take power in their own kingdom, various visitors arrive to investigate and have to prove themselves much like performers auditioning for the circus. The gods, the equivalent of modern superpowers, are represented by traditional clown types, with Poseidon as the classic clown with white costume and conical hat, while the Barbarian appears as a strong-man gymnast.

Pez himself, says Hunter, “is not Arturo Ui (Brecht’s satirical representation of Hitler) or Machiavelli. He has a kind of native wit and is more like Bottom than anything else”. We can sympathise with someone who wants to set up a brave new world. “Most of us would not want to welcome in some of the categories he excludes — drunken poets, sycophants, inspectors — but alarm bells ring when he starts cooking birds. He can’t resist the push to expand the empire.”

Hunter and O’Brien have made one significant change to the original text which the director hopes is “in the spirit of Aristophanes”. Peithetairos dispenses with Euelpides when he objects to his methods. In this version Eck comes back in the guise of various messengers, so continuing the dialogue between the two. For Hunter it emphasises the fact that “the rise to power starts with personal betrayal”.

While Magni, Carmichael and Bushell-Mingo are experienced actors, some members of the athletic company are new to theatre. They are being coached by Hunter to stay in character — not easy if you are trying to concentrate on not plummeting from a great height.

She is full of admiration for the discipline of her cast. Everyone trains for an hour-and-a-half each day as they go through “the pain and calluses involved in what seems light and effortless”.

Hunter recently spent six months working with Peter Brook in France. There the circus is treated more seriously, she says, so using big-top skills to tell a serious-comic story doesn’t seem so unusual. After The Birds concludes its run at the National, more people can judge the result when it tours in a big top around the country, including the Lowry in Salford and the Gardener Arts Centre in Brighton.

As Hunter and her cast prepare for the opening night, everyone is aware that this is one occasion when you don’t tell the performers to “break a leg”.