Bill Kenwright presents 'Pushing The Boundaries', the fourth in Radio 2's season of documentaries telling the story of the most popular and successful global form of theatrical entertainment, The Musical. The development of musical theatre is an on-going road of discovery and experimentation. Musicals offer an opportunity to push at the boundaries - something they have repeatedly done: not simply in the way that shows are staged but in the subject matter their stories tackle. This programme considers shows which deal with subjects considered as 'taboo'. This week's case studies are: 'Oh, What A Lovely War!', 'Hair', 'La Cage Aux Folles', 'Cabaret', 'Sweeney Todd' and 'Avenue Q', with interviewees including: Don Black, Stephen Sondheim, Angela Lansbury, Michael Grandage, Richard Stilgoe, Liz Robertson, James Rado, Liza Minnelli, Elaine Paige, Paul Nicholas, Jerry Herman, Cameron Mackintosh, Douglas Hodge, Hal Prince, Joel Grey and John Barrowman. 'Pushing The Boundaries' is written by Brian Sibley and produced by Malcolm Prince.