Novak Djokovic defeats Roger Federer 6-3 6-4

Novak Djokovic defeated Roger Federer in straight sets to win the ATP World Tour Finals championship for the fifth time on Sunday.

The world's top player won 6-3 6-4, breaking vitally in the final game of both sets, to land an 11th title of a dominant 2015. He also became the first player to win this event four consecutive times in a repeat of last year's final which Federer forfeited due to injury.

Federer had beaten Djokovic on Tuesday during the group stages at the O2 Arena, but the final of the competition was never truly close as the Serb always seemed likely to hold onto the early lead that he had forged.

The warning signs were there from the opening game when Federer was forced to save break point, roared on by a buoyant London crowd who made no apologies for clearly favouring the world No 3. In one early exchange, an over-enthusiastic fan drew the ire of Djokovic by shouting mid-point.

Federer held the opening game and established an early threat with Djokovic on serve - the world No 1 saved break point - but the first two games would prove the most competitive of the set. With Federer serving and coming to the net, Djokovic broke for 2-1 with a lovely backhand and that advantage was never threatened as the match wore on.

A big smash enabled Federer to roar through his third service game and then earned break point - it was the crucial moment of the first set as he failed to capitalise and Djokovic was let off the hook. The Serb would be less forgiving, breaking again as Federer served to stay afloat.

Djokovic's remarkable knack of winning vital points continued in the opening game of the second set - Federer made the crowd gasp with a backhand then a forehand winner to both corners of the court, yet still found himself unable to break.

The 17-time Grand Slam winner won the most sensational point of the match by ending a back-and-forth exchange with a big smash yet it still wasn't enough to prevent Djokovic holding his serve to go 4-3 up.

Djokovic opened three break points in the next game with two brilliant forehand winners but Federer dug deep to keep himself in the match, much to the crowd's unanimous delight. It would be his last moment of glory at the London tournament until next year.

Needing to hold his serve, Djokovic brutally opened two match points and broke again to win his fifth title at the O2 Arena.

The victory brought their overall head-to-head record to 22 wins apiece, while Djokovic has won five of their eight meetings this year. It represented an appropriate end to 2015, a year that brought three Grand Slam successes and established Djokovic as the world's greatest player.