Sue Barker presents live coverage of the group stages of the ATP World Tour Finals, which sees the top eight players in the world battling for supremacy in London. Despite Andy Murray's withdrawal through injury, the world's top two players Rafael Nadal and Novak Djokovic will headline a stellar cast. Djokovic beat Roger Federer to win 2012's crown, but French Open runner-up David Ferrer has been as high as third in the world rankings in 2013 and can't be ruled out. Show less