ATP World Tour Finals 2015 RESULT: Novak Djokovic retains trophy by defeating rival Roger Federer in straight sets

Thanks for joining me. Here's my colleagues report from the O2. Click on the link below to read it in full. 

Novak Djokovic capped the best season of his career - and quite possibly one of the greatest in the history of the sport - by defeating Roger Federer on Sunday to win the ATP World Tour Finals.

World No 1 Djokovic was too good for Federer with a 6-3, 6-4 victory at the O2 to end his year with an 82-6 record, 11 titles, including three Grand Slams. Let us not forget, too, that the Serb was just one win away from the Calendar Grand Slam, losing to Stan Wawrinka in the Roland Garros final.

This was the final that never happened last year when Federer was forced to withdraw shortly before he was due on court with a back injury suffered during a tumultuous semi-final battle against Wawrinka the night before. 

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Djokovic retains the ATP Tour Finals trophy

He's done it once again. Djokovic 22-22 Federer. The O2 crowd may not have liked it but Djokovic deserved his win. A challenge by Federer sees the result delayed but Djokovic eventually gets his hands back on the trophy. 

He's almost there. Federer has performed admirably but Djokovic really is a class above. A win for Djokovic would also see Murray finish the year as the world's No 2. A boost for Britain ahead of next week's Davis Cup. 

Djokovic had a number of opportunities to break Federer but you can never keep a good man down, can you? He manages to bounce back to claim the game and keep himself in the game. Game on.

Federer won the most impressive point of the match but he fails to take the game. Djokovic will have near enough two hands on the trophy if he can break his rival in the next game. 

Another incredible between the world's best. Djokovic manages to get his racket to the ball to launch it into the air but his effort is volleyed back at him and behind the court. Federer won the rally but can he break Djokovic and win the game?

Djokovic praises Federer once again after the latter's neat backhand volley from the net. Federer keeps himself in the match by taking the sixth game in the second set. It's tit for tat. 

You can see why Djokovic is the best in the world. A Federer at his peak may have been able to stop him but the ageing star looks like he will come up short once again today. A win for Djokovic would also see him level his head-to-head record with Federer. 

Just when you think Djokovic cannot respond to a Federer shot, he does. This time he stretches down to his right to drive the tennis ball past Federer. The Swiss does manage to take his service game despite Djokovic's ability to return pretty much anything. 

Federer looks far more comfortable now but still Djokovic is out in front. Despite two outstanding shots by the Swiss, he loses the third game in the second set. It seems like the O2 crowd will be going home in relative disappointment as their man looks like he could lose in straight sets. 

What a shot by Federer! You can tell it's good when Djokovic hits his racket to applaud. Federer plays a delightful backhand down the line, leaving Djokovic with no choice but to stand and stare. 

Federer's serves appear to have improved. Djokovic fails to successfully return his serve which results in Federer levelling the scoreline in the second set. 

Djokovic takes the first game in the second set. He finishes off the game with a fast-paced ace. 

Djokovic’s serve does not often get talked about but again it’s a major factor underpinning his game here and supremely functional. It has delivered four aces and a very high 77% first serve ratio. That is very hard to break, even if you are Federer.

Djokovic's base level is so high that even when he is not going all out for winners, it is so hard to break him down when his rhythm is so steady from the back of the court.

Federer's first serve percentage is also sitting down at 57%. When he's beaten Djokovic in the past, generally that number is sitting somewhere in the 70s.

Djokovic has one hand on the ATP World Tour Finals trophy. He doesn't look like he wants to let it out of his grasp after winning the competition on the last three occasions. He breaks Federer again to take the first set. His tactical approach is clear to see with the Serb drawing Federer to the net before either lobbing or smashing the ball out of his reach. 

Djokovic let's his opponent back into the game by hitting it long and wide on two separate points but he appears to be just toying with his rival. He eventually takes the game to take a 5-3 lead. He is closing in on the first set. 

The aforementioned tactic did not work on two occasions in the seventh game as Federer puts a spanner in Djokovic's works by coming to the net before slamming the ball home to take the last few. The advantage is still with the world No 1. 

Djokovic is so good at getting his opponent to come to the net before trying to hit the ball long. This time Federer manages to get there but his tactical ploy does usually. The seventh game currently stands at 30-15. Can Djokovic break his rival once again?

Djokovic takes the game to take a 4-2 lead. Federer pushed him all the way but Djokovic managed to muscle his way back into the lead. The O2 crowd are again showing their support for the underdog.

Federer makes it deuce with a driven backhand down the line. He was in the lead but Djokovic came back to take a 40-30 lead. 

Federer wins four straight points to take the fifth game, with the score now at 3-2 to world No 1 Djokovic. The Swiss will be desperate to both get his hands back on the ATP World Tour Finals title and also claim second spot in the rankings from Murray. 

Djokovic's dominance is already starting to show. Let's see if he can break Federer once again to move one step closer to claiming the first set. 

As you'd expect Federer enjoying all the crowd support. Djokovic reminds me of Ivan Lendl and Pete Sampras at stages of their career, when their high level of success was not matched by public adoration.

Djokovic gets the first break of the match to take an early advantage in this final. Federer is keeping pace with the world No 1 but you feel he could tire due to the amount of work he is already having to do on the court. Remember Federer is 34, while Djokovic is 28.

What a rally! Federer slides from left to right as he returns Djokovic's driven shots but manages to get the upper-hand over his rival by claiming the point. Both players are trying to dictate play from the baseline. Djokovic has just drawn Federer to the net before slamming the ball past him. 40-30 Djokovic in the third game.

It's all-square at the O2 with Djokovic winning his service game. Again the crowd show their love for Federer by jeering. 

Djokovic's serves proves to be too powerful for Federer during the first point. He then takes the second before Djokovic hits the ball into the net to make it 30-15. It now stands at 30-30 in the second game as Djokovic's wayward shot goes out. 

The Swiss star takes the first game. Federer takes the advantage before finishing the job with a powerful drive, which Djokovic fails to return. 

As my colleague Stuart Fraser previously said, the crowd are clearly with Federer. The fans make loud cheers after Djokovic plays the ball into the net to level the scoreline at deuce. 

Federer is serving for the first game. Djokovic wins the first point but Federer shows his undoubted class to win the following two. 30-15 to Federer. 

So can Djokovic level up his head-to-head record with Federer by winning tonight? Here comes the first game. 

You will be delighted to hear that there is no repeat of last year when Roger Federer was forced to pull out shortly before the final with a back injury. It prompted an emergency call to Andy Murray, who was on his couch playing Mario Kart at the time, to come in and play an exhibition match.

Both players walk out on to the court and no surprise that Federer receives the louder cheer. A lot of Swiss fans here and his popularity globally is so high. Djokovic well used to being the crowd's second favourite when he takes on Federer, to be honest.

Federer: 'I'm feeling much better than last year. I am very relieved. It is going to be really exciting to walk out. Novak has done an amazing job in getting fit and fast from the baseline. I am very clear how I want to attack and being indoors helps a bit.' 

Djokovic: 'It has been a long season but when you start the season you wish to reach the final match. I don't think anything significant will surprise one another tonight.' 

Who do you think will win tonight's final, Sportsmail readers? And will it go to three sets or be decided in the second?

Have your say in the comments box below or tweet me @Anthony_Hay

Djokovic was given a walkover victory during last year's final as Federer withdrew with a back injury at the last minute. 

Let's hope Federer can make up for last year's disappointment by putting on a show as he tries to wrestle the ATP World Tour Finals trophy back from Djokovic. 

Djokovic has won the last three ATP World Tour Finals in London, with Federer winning the previous two before the Serb's recent dominance. 

Roger Federer shocks Novak Djokovic by beating World No 1 in straight sets

Strutting around the O2 Arena like an unshaven avenger, Roger Federer caused what now almost constitutes a sensation by beating Novak Djokovic.

The 34 year-old Swiss shattered the defences of the normally impregnable world No 1 to beat him 7-5, 6-2 and thus put himself through to the semi-finals of the Barclays ATP World Tour Finals.

It was only Djokovic's sixth defeat of the season and the first he has suffered since August 23 in Cincinnati. It was also his first on any indoor court in just over three years, and a packed crowd of 17,000 loved all 77 minutes of it.

READ MORE OF MIKE DICKSON'S REPORT FROM TUESDAY'S MATCH HERE

Hello and welcome to Sportsmail's live coverage of tonight's ATP World Tour Finals final between world No 1 Novak Djokovic and world No 3 Roger Federer.

Federer managed to spring a surprise against Djokovic on Tuesday by beating his rival 7-5, 6-2.

The Swiss star still has a chance to overtake Andy Murray by moving into second spot in the rankings behind Djokovic.

However he will have to both win tonight and hope Murray fails to shine in next week's Davis Cup final in Belgium.

Meetings between the pair have often been extremely tight, with Federer holding the edge with 22 wins to Djokovic's 21.