Dandy Andy rules the world after convincing conquest of Djokovic

His season had already provided several unforgettable chapters, but Andy Murray saved the best for last as he eclipsed Novak Djokovic 6-3, 6-4 to claim his first ATP World Tour Finals title and rubberstamp the year-end top ranking on Sunday.

Against a man who has so often been his nemesis, Murray produced a relentless display to claim his ninth title of a year that included a second Wimbledon crown and Olympic gold in Rio.

The Scot's play in the winner-takes-all season climax was all the more remarkable as a day earlier he looked on the point of mental and physical exhaustion after taking almost four hours to subdue Canada's Milos Raonic in the semifinal.

Andy Murray celebrates winning a rally against Novak Djokovic during Sunday's ATP World Tour Finals at O2 Arena in London. Toby Melville / Reuters

It would have been a crushing blow if, two weeks after dislodging Djokovic from the top ranking, the Serb had ripped it back with a fifth consecutive Tour Finals title.

But Murray's powers of recovery appear limitless as he handed an error-prone Djokovic a bitter defeat that will leave a sour taste in the 12-time Grand Slam champion's mouth as a new season swings into action in a few weeks.

Murray double-faulted twice in the first game and there was a wobble near the end as Djokovic mounted some late resistance, but with the majority of the 17,000 fans in the O2 Arena willing him on, Murray completed the job.

"It's very special playing against Novak in a match like this. We've played in Grand Slam finals and at the Olympics before, but I am very happy to win and to be world No 1 is very special. It is something I never expected," Murray said.

His win came two days after older brother Jamie was crowned No 1 doubles pair with Brazil's Bruno Soares and a year since Britain captured the Davis Cup title.

Djokovic had won 22 of his past 23 matches at the Thames-side venue, but the cracks that have appeared in his game since completing a career slam by beating Murray in the French Open final returned after a trouble-free route to the final.

The Serb made 30 unforced errors, and some of his mistakes were worthy of world-class criticism.

Despite his year tailing off, however, and losing a 9,000-point ranking lead over Murray, Djokovic still won seven titles and finally ruled at Roland Garros.

He was gracious in defeat.

"Definitely he is the No 1 in the world. Andy is the best player and deserved to win," said Djokovic.

"He played the better tennis in the decisive moments. Credit to Andy for being mentally tough."

Sunday's clash hardly needed hyping, with the world's two dominant forces colliding on a spectacular indoor court to contest the last match of the ATP season with the No 1 ranking to be decided.

It had never happened before in the tournament's history.

The fear was that the 10 hours Murray spent on court during the week, compared to Djokovic's six and a half, would catch up with him and snap a career-best winning run of 23 matches.

Despite some early nerves, Murray quickly put those fears to bed, dictating the rallies with unerring length and precision.

For his part, Djokovic looked inhibited and hesitant.

It took him 10 minutes to hold serve at 2-3 - a game in which he blazed one smash wildly wide from virtually over the net.

Murray was at Djokovic's throat again at 3-4 and Djokovic buckled, feebly dropping serve before Murray sealed the set with another rock-solid service game.

The final threatened to become a humiliation for Djokovic as Murray steamed into a 4-1 lead in the second set.

He gave himself a flicker of hope with a break and a hold, and the crowd quietened a little as Djokovic began swinging dangerously, winning one hypnotic 33-stroke rally before Murray dug his heels in to lead 5-3.

Two match points came and went at 5-4, but Murray's coronation as No 1 was finally confimed when Djokovic lamely floated a soft return wide on the third.

The doubles title was won by Australian John Peers and Finland's Henri Kontinen who beat Raven Klaasen and Rajeev Ram.

No 1 expects his best years still to come

Andy Murray believes the best years of his career could still be ahead after confirming his status as world No 1 by beating Novak Djokovic to claim the ATP Tour Finals crown on Sunday.

Murray, 29, became the oldest man since 1974 to reach the top of the rankings for the first time last month and the way he dominated the final months of the season, winning five titles and 24 matches in a row, suggests he could be right.

"I obviously want to try to achieve as much as I can these next few years because I'm not going to be around forever," Murray said.

"These next few years, I want to try to make them the best of my career. But it's going to be tough."

Had Murray lost to Djokovic on Sunday and relinquished top spot two weeks into his reign the chances are he would have overhauled the Serb again next year as he has fewer ranking points to defend in the months after the Australian Open.

Having scaled the summit earlier than he expected, Murray might well take some shifting.

"I would like to try to stay there. It's taken a huge effort the last five, six months," he said.

"I'm aware that's going to be extremely difficult. But now that I've got there, I obviously would be motivated to try to stay in that position.

"But the majors are what gets me working hard and what really, really motivates me."

First, however, Murray will afford himself the luxury of a short rest after a grueling week in London where he twice set a record for the longest match in the tournament's history.

On Saturday, he spent three hours and 38 minutes defeating Canada's Milos Raonic, two days after beating Kei Nishikori in another three-hour epic in the group stage.

He admitted he was running low on energy against Djokovic as the Serb staged a late rally.

"I didn't feel great this morning in practice. I was hitting the ball fine, but just a bit sluggish, a bit heavy-legged," Murray said.

"Thankfully, in the first seven games of the match, there were no long rallies, which for us is strange. It wasn't until the middle of the second set when the rallies started to get extended that my legs were really starting to feel it."