I can’t think why St Trinian’s fell out of fashion. It is the greatest public school Ealing ever invented. I wanted to board there at the age of 8, utterly ignorant of the fact that Frank Launder and Sidney Gilliat’s 1950s films simply put human flesh on Ronald Searle’s scandalous cartoons. The girls – actually “gals” on the scratchy black-and-white originals – were vaguely saucy, heroically nonconformist, and shared a knack of waving hockey sticks and getting away with blue murder.

Oliver Parker’s high-heeled version of St Trinian’s is a spiky, topical joy. Despite the micro-skirts, fishnet stockings, and catwalk models, including Lily Cole, the raunch factor rarely exceeds a Carry On tease. But the 2008 female clans are neatly mapped out when new girl, Annabelle (Talulah Riley), is paraded past emos, geeks, posh totty, chavs and first year sopranos.

Every one of these girls is guilty until proved innocent, and the hardline Mr Clean-up is Colin Firth. St Trinian’s is a disciplinary disaster area. The teachers’ common room resembles a Soho dive bar. The exam results are a national disgrace. The chemistry lab is a vodka distillery. The school encapsulates all the evils of private education. And Firth is determined to destroy this carbuncle on the bottom of the education system in the full glare of television lights and the tabloid press.

The plot – to save the school from scheming bastards – is frankly old hat. But Colin Firth’s humiliation is a thing of wonder. His entire career on screen and stage is beautifully sent up before our eyes. The bête noire is the utterly fabulous headmistress, Camilla Fritton, played by Rupert Everett. Her toothy smile is probably less pleasing than it was yesterday, and her bosoms have anchored around her waist. But the old fruit has a hold over Firth that no film, actor, bit-part player or contract can possibly deny. They were lovers at Oxford. “It was another time,” murmers Miss Fritton, licking her teeth. “It was Another Country,” sighs Firth.

I’m afraid the film-spotters’ entries multiply as Firth is tossed into a fountain (Bridget Jones), humped by a dog called D’Arcy, thrown into a lake (Pride and Prejudice), forced to explain the theft of Vermeer’s Girl with a Pearl Earring, and caught naked by the tabloids throwing open the curtains in a room he shouldn’t be in (Life of Brian).

Certificate 12A, 101mins

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