As one sporting great retires and another adds to her gold medal tally at the Paris Olympics, the Sky News Daily profiles Andy Murray and Simone Biles.    Liz Bates speaks to sports journalist Sue Mott who helped Murray write his autobiography.    She's also joined by Kathy Williams, who became the first black female gymnast to represent Great Britain at an Olympics, in Los Angeles in 1984.   Kathy talks about why Simone Biles has become one of the greatest Olympians of all time.  Producers: Tom Pooley and Rosie Gillott Editor: Paul Stanworth  Promotion producer: David Chipakupaku