Novak Djokovic beats Rafael Nadal to win World Tour Finals

Novak Djokovic retained his ATP World Tour Finals title with a convincing win over world number one Rafael Nadal. The Serb, who lost the top ranking to Nadal last month, won 6-3 6-4 at the O2 Arena in London. via Pocket http://www.bbc.co.uk/sport/0/tennis/24894117