Sue Barker presents live coverage of the top eight tennis players in the world going head-to-head at the ATP World Tour Finals in London. Despite Andy Murray's withdrawal through injury, the world's top two players Rafael Nadal and Novak Djokovic will headline a stellar line-up. Nadal has never won the end-of-season showdown but has taken his Grand Slam titles total to 13 this year and will be the man to beat at the O2 Arena. Show less