Mark Lawson talks to leading theatre producers, including Cameron Mackintosh, Howard Panter and Rosemary Squire, Andrew Lloyd Webber, Bill Kenwright and Sonia Friedman, about the art of creating a hit show. The theatre impresarios discuss the impact of having a successful show and how long running productions such as Les Miserables and The Phantom of the Opera changed the theatre industry. Along side the hits, the producers talk about the millions of pounds lost when they have a flop; and they address the criticism that ticket prices are often too high. Producer Claire Bartleet.