Novak Djokovic beats Rafael Nadal to win World Tour title

Novak Djokovic retains his ATP World Tour Finals title with a resounding win over world number one Rafael Nadal.

The Serb wins 6-3 6-4 at the O2 Arena in London extending his unbeaten run to 22 matches.

Nadal has yet to win the season-ending finale, Djokovic has now won it three times.