Ragtime

The leafy glades of England's loveliest park theatre are a bizarre place to kickstart an American president's re-election campaign. But here is Obama, beaming audacious rays of hope down from a colossal 'Dare to Dream' poster, which crowns the heap of rubble and broken shop signs that designer Jon Bausor has fly-tipped in the midst of this sylvan arena.

Those who've come for a lovely night in a lovely place will probably be boggled by the fact that the USA commercial-industrial complex has apparently taken a big concrete dump all over the stage. But the venue's vigorous boss Timothy Sheader, who has revived this gritty 1998 musical about the growing pains of fin de siècle America, seems determined to give us a powerful night wrapped in a picturesque one.

'Ragtime: the Musical' is based on EL Doctorow's panoramic 1975 novel about immigration, racism and jazz. It's a weird, brave choice for one half of a two-show Olympic summer rep season - though it may just swing the American tourist vote. Un-English, unpastoral, unromantic and unfocused, it offers a tough liberal allegory of America's troubled racial and social identity instead of the usual love and glamour. Its grit and pertinence are relentlessly in-your-face in this staging, in which a rainbow-coloured gang of scruffy modern citizens step out of their pink velour track-pants and blue jeans and go back in time to embody the numerous symbolic characters, which include a Wasp family, a pair of starving Jewish immigrants, an oppressed black couple and Houdini.

I never worked out exactly why they all emerge from a post-apocalyptic rubbish dump. But Sheader's production grows in strength and packs sublime lung power. Rosalie Craig's radiant white 'Mother', dressed in stars and stripes, triumphs over the Open Air amplification, which can sound blurry and synthetic. And there are gorgeous cameos from Katie Brayben as a plumptious burlesque star on a swing, and Sophia Nomvete as pioneering black politician Booker T Washington.

Stephen Flaherty's music is potent and ambitious. But ragtime is a jaunty come-hither style whose rhythms create a nicely restless soundtrack for a society in flux, but is less good at underscoring racist murder and attempted infanticide. It's not all downbeat. Brangelina would love the ending - in which Craig's lovely 'Mother' figure acquires a multi-ethnic family that could be a poster for tolerance and unconditional love. Sheader's production doesn't take itself too seriously and is ultimately uplifting . But that riven poster image of Obama above is a bleak reminder that, even in a show that could be subtitled 'Dreams of My Fatherland', one person's dreams are another's nightmare.