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.
Djokovic, 26, extended his unbeaten run to 22 matches as he claimed the season-ending title for the third time.
He will now head to Belgrade, where Serbia take on the Czech Republic in the Davis Cup final from Friday.
Nadal might have earned the year-end number one ranking after his remarkable return from injury in February, but Djokovic denied him a first ATP Finals title and laid down a marker for battles to come in 2014.