For decades, one of Britain's best-known entertainers, the late Jimmy Savile, sexually abused children and vulnerable adults and got away with it. In response the police launched a massive effort to investigate allegations of historical sexual abuse. Other prominent people found themselves facing accusations. Stephen Sackur speaks to one of them: broadcaster Paul Gambaccini spent a year as a suspect before the case against him was dropped. What lessons can be learned from what Gambaccini calls 'twelve months of trauma'?