Spinning out its screwball premise with dexterity and wit, hugely engaging British romcom Man Up is a winner all the way.

Snarky singleton Nancy (Lake Bell) and emotionally bruised divorcee Jack (Simon Pegg) meet cute beneath the clock at Waterloo Station when he mistakes her for his blind date. Rather than disabuse Jack of his error, Nancy spontaneously decides to impersonate the woman he is expecting to meet (Ophelia Lovibond’s unquenchably perky 24-year-old triathlete), setting in motion a series of escalatingly zany events.

The film barrels along around a refreshingly down-to-earth, un-touristy London with a giddy momentum that is exhilarating. That said, Rory Kinnear is a little too creepy for comfort as a deranged stalker who used to be Nancy’s schoolmate and Olivia Williams is rather short-changed as Jack’s sour ex-wife. But first-time screenwriter Tess Morris supplies a steady stream of sharply observed gags and Bell and Pegg ensure their characters remain both credible and likeable.

The duo’s chemistry is sensational, too, with American Bell nailing her English accent perfectly and Pegg redeeming himself after such recent flops as Hector and the Search for Happiness and Absolutely Anything.

Certificate 15. Runtime 88 mins. Director Ben Palmer.

Man Up is released on Blu-ray & DVD by Studiocanal.