Sue Barker presents live action as the best men's players on the planet do battle in the final act of the 2013 season, the ATP World Tour Finals in London. Andy Murray will not be at the O2 Arena due to injury, but there is no shortage of talent with the world's top-ranked players Rafael Nadal and Novak Djokovic both heading to the capital. Djokovic is the defending champion having beaten Roger Federer in straight sets in last year's final, but his Spanish rival Nadal is the form man in world tennis. Show less