Sir Cameron Mackintosh was once a theatre stagehand on Drury Lane and is now a musical theatre impresario, with a career spanning 50 years and a catalogue of musical theatre hits to his name - including Cats, Les Miserables, Phantom of the Opera and Miss Saigon, and he is now about to launch the US hit musical Hamilton in London.Alan Yentob meets Cameron Mackintosh to discover how a timber merchant's son with a passion for song and dance, an abundance of ambition and a keen eye for detail became the most successful man in the musical theatre business and in the process changed the face and sound of musical theatre across the globe.