Michael Caine is the biggest movie star Britain has ever produced - indeed, his life story is the story of Britain in the twentieth century. Born into South London poverty during the depression-hit 1930s, Caine as a child suffered the depredations of war and then wasted his youthful energies fighting in Korea during the fifties. Subsequently he began his long, slow climb up the greasy pole of the acting trade (a walk-on in ''Pinter'' here, a bit-part with Stanley Baker there.) But following the Suez crisis, as Britain's old order began to crumble, Caine's gritty working class credentials came into their own through a string of mould-breaking roles: the Old Etonian who no longer believes in his power to command in ''Zulu''; Harry Palmer, the cashiered NCO who lives for his insubordinate detestation of the upper classes in ''The Ipcress File''; Alfie, the last hysterical macho in a culture about to be wrong-footed by feminism; and Charlie Croker, the vicious Little Englander out to do de Gaulle's Europe down in ''The Italian Job''. But Caine is far more than just a sixties icon.Throughout his four decades as an international star he has continued to echo his country's mood-swings: in the seventies with the Tyneside-set thriller ''Get Carter'', a brutal riposte to the summer-of-love years; and in the eighties with the Thatcherite get-rich-quick squalor of ''Mona Lisa''. In the nineties, this son of a Billingsgate fish porter would become Sir Michael Caine - the living embodiment of John Major's much-vaunted 'classless society'. Combining anecdote with history, critical analysis with wit, Christopher Bray's book - the first serious critical biography of Michael Caine - is a class act in itself.