Murray remains world No 1 after beating Djokovic at the O2

Andy Murray has finished the year as world number one after beating Novak Djokovic in straight sets to win the World Tour Finals.

Murray reached the top of the tennis rankings during the Paris Masters two weeks ago - but would have been knocked back down had Djokovic beaten him at the O2 Arena in London.

Fans' nerves were calmed though when they saw that the Wimbledon champion was in ominously good form, taking the first set 6-3, the second 6-4.

It means the Briton's winning run has now reached 24 matches.

It was also his fifth straight title.

This was the first time that the number one spot had been decided by the final match of the tennis season.

Djokovic, who had won 24 of their 34 previous meetings, had described the contest as one of the biggest they would ever play.

Going into the match, the Serb appeared to have an advantage after dispatching Kei Nishikori in little more than an hour during their semi-final.

In contrast, Murray had battled for three hours and 38 minutes against Milos Raonic.

But Murray never looked seriously threatened on Sunday, while Djokovic made some uncharacteristic unforced errors.

Speaking afterwards, Murray said: "Obviously it's a very special day.

"Playing against Novak in a match like this, we've played grand slam finals, Olympics, it's been a tough rivalry.

"I've lost many of them - I'm very happy I managed to win today. To finish the year number one is something I never expected."

Murray also thanked his team, saying: "I couldn't do it without them."

Murray's elevation had been unexpected earlier in the year - especially after Djokovic had beaten him in the final of the French Open.

At that stage, Djokovic held all four grand slam trophies.

But the 29-year-old Serb has won only one tournament since.

Nevertheless, he did not sound downhearted.

"It's been a fantastic year," Djokovic said.

"Obviously there's a lot to look back to - great highlights, especially in the first six months.

"Today we were both part of history. It was an honour to be on the court."

Djokovic added: "Andy is clearly number one of the world, he's the best player. He played the best tennis in the decisive moments.

"I wasn't able to come back. I started playing a bit better but it was too late. I congratulate Andy and his team for a great year."