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Djokovic made a perfect start to the match when he held onto his own serve with ease before taking advantage of the second of three break points in Nadal's opening service game.
The world number one fought his way back into the set with a break of his own in the fifth game, being helped on his way by a wild Djokovic forehand.
Djokovic broke back in the eighth game after some impressive returns and a particularly exciting exchange between the two players at the net, before going on to hold his serve and clinch the opener 6-3.
Once again the Serb struck early in the second set, breaking Nadal in the third game having raced into a 40-0 lead before sealing it at the third time of asking.
Djokovic squandered a match point in the penultimate game as Nadal battled back from 40-30 down on his own serve to prolong his stay in the match for at least one more game.
That was all it proved to be, however, as Djokovic clinched his second consecutive ATP World Tour Finals title in London by serving out the match.