In many ways Gigi is the dark My Fair Lady. We all remember the loveable 1958 film with Maurice Chevalier thanking heaven for little girls and Lesley Caron in her sailor suit capturing rich playboy Gaston but for all the froth, there is a cynicism, a cruelty to the classic Lerner-Loewe musical.

It’s based on Collette’s novelette (about the “unsentimental” education of a young Parisian girl). Where Pygmalion showed an artless working-class girl turned into a lady, Gigi illustrates the reality of a vivacious 16-year-old being groomed to become a courtesan by the women of her family. They’re not willfully cruel, just pragmatic. Women have no currency except to be bought and sold. A poor woman cannot afford ”a semi-precious romantic oblivion”.

Alan Jay Lerner wrote the book for both Gigi and My Fair Lady and Gigi is witty, camp, extremely entertaining. Set in 1901, the new production brilliantly captures the whole belle époque – the champagne, the parties, the trips to the seaside. Thanks to designer Yannis Thavoris’s cartoon set, Paris becomes a satellite of Maxim’s famous restaurant. Nobody works (“Occupation? 100 per cent leisure”); infidelity is a joke; mistresses change hands more often than Alsace Lorraine. And sex is a transaction between (powerful) men and (impoverished) women.

The cast is borderline eccentric — with Oscar winner Topol as Honoré (the Chevalier role), Millicent Martin (last seen in Frasier) as Gigi’s grandmother and Avengers girl Linda Thorson as her scheming aunt. But suspend your snobbery: this is pantomime with an edge.

“Why are we laughing at this casual misogyny?” asked my (male) companion at the interval. Why indeed? You hope that Aunt Alicia’s mercenary advice (“It’s easier to imagine wonderland with a floor-plan in your hand”) is ironic. But when they auction Gigi off to Gaston — with a celebratory dance —it is genuinely shocking. It is only thanks to Lisa O’Hare’s delightfully truculent Gigi that we care what happens to her.

But in the last scene, Gaston (a winning Thomas Bouchert) sees himself for the shallow player he really is. The musical ends in marriage and costume changes – but the tone has shifted. We’ve moved beyond the stylised glamour of the famous MGM movie to something rather more interesting.

Until 13 September (0844 826 4242).