Mark Lawson talks to novelists who have taken on another writer's characters, including P D James, who wrote a Pride and Prejudice sequel, Anthony Horowitz, creator of a new Sherlock Holmes story, Jeffery Deaver, author of the latest James Bond book, and Frank Cottrell Boyce, who took on another of Ian Fleming's creations - Chitty Chitty Bang Bang.

And what happens to a novel left unfinished when a writer dies? Incomplete manuscripts left by British novelist Beryl Bainbridge and American writer Michael Crichton were posthumously brought to publication this year, with the help of editor Brendan King and scientific journalist Richard Preston respectively. They discuss how they approached this poignant task, and A N Wilson, writer and friend of Beryl Bainbridge, reflects on the process.

Producer Katie Langton.