Mariella Frostrup interviews Andrew Morton, the author of Diana: Her True Story, a biography of the Princess of Wales that was published in 1992. The book caused huge controversy when it was serialised in the Sunday Times, as it offered an intimate insight into Diana's personal troubles and her experiences of life in the royal household - but it was only after her death in 1997 that Morton revealed she had been the source for much of his information. In this programme, he reveals how he was shunned by fellow journalists and received death threats from terrorist groups, and why he sought a statement of support from the princess as he tried to restore his reputation