Andy Murray will finish 2016 on top of the world rankings after an imperious 6-3, 6-4 victory over Novak Djokovic clinched his first ATP Tour Finals title on Sunday.

Murray had ended Djokovic's 122-week reign as world number one two weeks ago and his triumph in their winner-takes-all clash at London's O2 Arena stopped the Serb regaining pole position.

The 29-year-old is the 17th man to hold the prestigious year-end number one berth since the inception of the ATP rankings in 1973.

He is the first player other than Djokovic, Roger Federer or Rafael Nadal to earn the honour since Andy Roddick in 2003.

Soaking up the acclaim from a star-studded 17,000 sell out crowd including actors Jude Law, Kevin Spacey and Woody Harrelson, Murray said: "I'm very happy to win and to be world number one is very special. It's something I never expected.

"We've played Grand Slam finals before but it's very special playing against Novak in a match like this."

Djokovic added: "I played better late in the match but it wasn't enough.

"Andy is definitely number one in the world. He deserved to win. He is the best player."

Murray will bank the champion's cheque worth £914,000 ($1.1 million, 1.06 million euros), but the financial reward pales in comparison to the sense of achievement that will accompany the tenacious Scot's 24th consecutive victory.

Ruining Djokovic's bid to return to the top caps an incredible year for Murray, who has won Wimbledon for the second time, claimed a second Olympic gold medal and become a father for the first time.

It is Murray's fifth consecutive title and the 44th of his glittering career, and with Federer and Nadal both seemingly in decline due to injuries, the Scot will believe he can reign at the top well into 2017.

For Djokovic, a strangely tame loss, featuring 30 unforced errors, will spark renewed questions about the world number two's sudden decline.

The 29-year-old has been in a prolonged slump since winning the French Open for the first time, prompting rumours about his private life and jibes about his recent involvement with a 'spiritual guru'.

After surrendering his four-year reign as Tour Finals champion with little resistence, he will be firmly under the microscope next season.

Djokovic had won 24 of his 34 previous Tour-level meetings with Murray, including the finals of this year's Australian and French Opens, and had lost to the Scot only twice in 15 matches since 2013.

However, that encounter at Roland Garros in June has proved a significant turning point for both men.

- Surge to the top -

Djokovic had spent months stuck in an unexpected rut, while Murray enjoyed the best six months of his career.

Even so, by the time they walked on court on Sunday, many expected Murray's surge to falter at last.

He should have been running on fumes after spending almost 10 hours on court this week, including surviving the longest match in tournament history against Milos Raonic in the last four on Saturday.

In contrast, Djokovic was well rested after taking three and a half hours less than Murray to reach the final.

But Murray is one of the sport's most intense competitors and he sent a message that he was ready to drag his aching limbs into battle one last time when he won a lengthy rally on the second point of the match.

Murray looked remarkably fresh as he glided around the court, working Djokovic into enough awkward positions in the fifth game to earn two break points.

Djokovic saved them both but it had taken him 10 minutes to hold serve, including one embarrassingly bad missed smash, and Murray's pressure paid off in the eighth game when he induced a tame forehand into the net from the world number two on break point.

Murray needed no encouragement to press home his advantage and quickly served out the set.

Some of Murray's greatest moments, his first Grand Slam title and first Wimbledon success, came at Djokovic's expense and so it was again.

He was hitting harder and with more variety than the Serb and he landed another huge blow with a break in the first game of the second set.

Djokovic was reeling and Murray showed no mercy with another ruthless break for a 4-1 lead.

With the finish line in sight, Djokovic got one break back, but Murray quickly regained his focus to seal one of the best wins of his life.