Magnificent Andy Murray beats Novak Djokovic to win ATP World Tour Finals title, stay No. 1

The Briton knew he had to beat the reigning champion 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 the Scot 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.

A pair of double faults in Murray's opening service game set alarm bells ringing but he benefitted from some cheap unforced errors from the Serb to hold.

From there the match began to live up to its billing with Murray the major aggressor. The Scot turned the screw in a wonderful seventh game where he saw the 12-time Grand Slam champion fend off two break points with some extraordinary defence.

The momentum was with the Briton and he made it count on Djokovic's next service game, unleashing a wonderful crosscourt forehand to break from deuce. Murray then served it out with a flourish to conclude a superb set of tennis where his forehand did most of the damage.

Djokovic had shown signs of nerves with an array of uncharacteristic errors and he leaked them again as Murray drove home his advantage by breaking at the very start of the second set at the fourth opportunity. A comfortable hold to consolidate notched up a fifth game in a row for the Scot and he continued to dominate as the number two seed struggled to hit the lines.

The Murray forehand was firing on all cylinders and he snared a double break to move 4-1 ahead. Djokovic finally responded and snatched a break back as the world number one began to show signs of tiredness for the first time.

Murray's exploits and resilience throughout the past seven days have illustrated he is a true champion who is difficult to defeat, and he held firm as Djokovic began to strike the ball freely. The Scot served for the title but saw Djokovic save two championship points before Murray finally capped his rise to the very top - and extend his career-best winning streak to 24 matches - when the Serb fired a return long.