How clever of director Stephan Elliott to cast Jessica Biel in Noel Coward’s critique of English snobbery. Her character, the fast, American “floozy” Larita, proves a near match for the hostile aristocratic clan whose son she has married.

And Biel, formerly a mere decoration in blockbusters and on Justin Timberlake’s arm, here gets her Yankee choppers into Britfilm royalty, Kristin Scott Thomas and Colin Firth. Her feisty performance stops Elliott’s film from being the by-the-numbers Twenties period drama it resembles.

The usual costume drama clichés are smoothly deployed. A magnificent motor car brings Larita — she is, shockingly, a racing driver — and puppyish hubby John Whittaker (Ben Barnes) up to a magnificent house.

Inside, John’s two silly sisters, several dogs, and lots of snobbery and barbed Cowardian aperçus await the new wife. John’s father (Firth) has let the estate go and his steely mama Veronica (Scott Thomas) is adamant her son should ditch his bride and knuckle down to save his inheritance.

Firth plays a man who has lost his soul, somewhere between the carnage of the trenches and the brothels of postwar Paris, with his habitual diffidence. Scott Thomas, looking heroically dowdy, goes into froideur overdrive.

Veronica is a character whose aim — keeping her family and estate together — might be admirable, even if her waspish methods are not, yet Scott Thomas plays her as if determined not to elicit a jot of sympathy. She is unremittingly brittle and icy, like mint cracknel. This unbalances Coward’s social point, which is delicately rather than savagely made.

Biel exudes the warmth and can-do vigour of an American adventuress, but is also touchingly hurt and bewildered in the face of snubs, slights, and the wearying business of behaving “properly”. Her relationship with Barnes’s pretty but insipid John never quite convinces.

Partly this is because Elliott makes him trill lines from period songs to Larita now and again, as if he’s suddenly been possessed by the soundtrack. Elsewhere, there’s a nicely judged comic cameo from Kris Marshall as the butler, and handsomely-mounted set pieces: a foxhunt with Larita on a motorbike, and a party where scandal is whipped up by a defiant tango.

This film is never less than lovely to look at. But it’s lifted above the level of being pretty, witty and mildly diverting not by those heavyweight Brits doing their thing, but by Biel.

Easy Virtue screens tonight as part of the London Film Festival at Rich Mix, 35-47 Bethnal Green Road, and goes on general release on 7