Class on stage: Charlie and the aspiration factory THERE are several ways of retelling "Charlie and the Chocolate Factory." In 2005 Hollywood focused on Willy Wonka, the factory's owner, portraying him as a purple-gloved man-child. A new musical production of Roald Dahl's children's story at the Theatre Royal in London concentrates on the up-from-poverty fortune of Charlie Bucket, the boy who finds the golden ticket. Mr Wonka lurks in beggar's dress at the side of the stage, as if selecting a specimen for a social experiment. Tales of upward social mobility attempted or achieved are crowding the London stage. "Billy Elliott," the story of a miner's son who contends with bereavement, strikes and the north-south divide to make it as a ballet dancer, recently celebrated its four-millionth visitor. "Port," an account of a Stockport girl's attempts to escape her grim origins, was a success at the National Theatre this spring. Last year "In Basildon" depicted strivers in the quintessential upwardly-mobile Essex town. It is a venerable theatrical (and literary) theme, but it is being handled in a different way. John Osborne's 1956 play "Look Back in Anger" showed a working-class man's fury at the middle class he had married into. By the 1970s and 1980s writers were looking down their noses at social climbers, in plays like "Top Girls" and "Abigail's Party," in which a middle-class arriviste serves cheesy nibbles and the wrong kind of wine. Social mobility receded as a topic for a while, as playwrights like David Hare turned to scrutinising the state of the nation. Now it has returned - and is depicted much more sympathetically. Dominic Cooke, who directed "In Basildon" at the Royal Court Theatre, says this may be a delayed reaction to the collapse of state socialism in Europe. Left-wing writers can no longer look to an alternative ideal. Instead they focus on how people navigate British society. A possible reason for the sympathetic tone is that upward mobility can no longer be taken for granted. In 2011 researchers at the London School of Economics concluded that intergenerational social mobility, assessed by income for children born between 1970 and 2000, had stalled. Another study, by Essex University academics, found matters had not improved during the slump. So it is fantastic fun to see people make it. Charlie Bucket does so spectacularly. At the end of "Charlie and the Chocolate Factory" he is a pint-size entrepreneur, with an immigrant workforce of Oompa-Loompas to ensure he does not tumble back down the social ladder.