Andy Murray won the ATP World Tour Finals title and ensured he finishes the year as world number one with a 6-3 6-4 win over Novak Djokovic at the O2.

The Briton knew he had to beat the reigning champion to fend off his arch rival's challenge to remain top of the rankings, and he produced a scintillating display to triumph 6-3 6-4 in one hour and 43 minutes.

It was a tour-leading ninth title of a remarkable season for Murray, who adds this prestigious crown to those won at Wimbledon and the Olympics.

Djokovic had seen his 122-week reign at the tennis summit come to an end just a fortnight ago at the Paris Masters, and both players came through this week to ensure the final would make history as the first to decide the year-end No.1.

Murray had lost 13 of his previous 15 meetings with Djokovic, including the French Open final six months ago. Since then Murray has been on a sensational run, but many felt his true claim to being top dog would only be tested by facing Djokovic.

This result provided the evidence, if it was needed, that he is currently the best in the world and perhaps suggests the balance of power has shifted his way.

Obviously it's a very special day, that I am playing against Novak in a match like this," Murray said.

"We have played Grand Slam finals, Olympics, matches like this... Its been a tough rivalry

"To finish the year as number one is something very special which I never expected."

Murray's performance belied the fact that he had set two new records for the longest matches in the tournament's history to set up what was arguably the most anticipated conclusion to a season finale ever.

There were concerns that fatigue may be a crucial factor heading into the much-hyped contest, with Murray having played almost three and a half hours more tennis than Djokovic en route to the final.