HARDtalk

Stephen Sackur talks to mental health campaigner Chris Costner Sizemore, who has been described as the most famous psychological case study in history. Growing up, her young mind was inhabited by a host of different personalities. Her extraordinary experiences gave rise to a newly-defined mental illness - multiple personality disorder - and her story was turned into an Oscar-winning film. Five decades after the initial diagnosis, are we any closer to understanding the mysterious rise of the alter ego?