Sarah Dunant and guests tackle the subject of incest. Mary Hamer's new book, Incest: a New Perspective, explores everything from the neurological damage incestuous relationships are said to cause, to the portrayal of incest in film and literature. Sarah Dunant talks to Hamer and others about whether we are any closer to being able to understand this most taboo of subjects and explores Hamer's thesis that incestuous abuse is the price paid by a society that insists on clear norms of masculinity and femininity.