Roger Federer overcame a late blip to win his sixth World Tour Finals title in his 100th final as a professional with a three-set victory over Jo-Wilfried Tsonga at the O2 Arena.

The Frenchman ultimately had an inconsistent first serve to blame for his defeat, with a booming forehand unable to undo the damage as Federer took advantage of his opponent's second serve to close out a 6-3 6-7(6) 6-3 success and pass his childhood idol Stefan Edberg's record of 806 professional victories.

"I couldn't be more happy, I couldn't be more exhausted," Federer said afterwards. "I can't be happier with the way the season has finished."

It was always likely to be close contest, after the pair had enjoyed a similarly draining three-setter to kick off the round-robin stage of the competition - won by Federer, after Tsonga had triumphed in a memorable five-setter at Wimbledon in the summer.

The first set gave little early indication of how things would ultimately pan out, however, with Tsonga dropping just a single point from his first two service games as Federer was made to work far the harder to stay on level terms.

But the momentum swung as soon as Tsonga's previously rock-solid first serve began to crumble, with the Swiss feasting on his weaker second serve to create a first break point opportunity that was only denied after Tsonga unleashed a perfect cross-court forehand to retain parity.

Federer would not be denied for long, however, as in the Frenchman's very next service game he was finally broken - after a trademark passing shot set up three breaking points, of which he only needed one.

The first set went with serve from there, but Federer was making things increasingly awkward for Tsonga on his own serve - forcing him to save two break points to prevent falling into another hole early in the second stanza.

Federer's probing eventually brought results, however, as he created another break opportunity with the scoreline reading 2-2 after a fine chip shot. The opportunity became an even better one after Tsonga fired his first serve into the net, and a blistering forehand down the line put the 16-time grand slam champion within touching victory of another tournament victory.

With the score having progressed to 5-4, Federer was given the first chance to serve for the championship - but the match would suddenly see a profound shift in momentum. Necessarily aggressive play from Tsonga enabled him to create three break points, although Federer kept his cool to save the first two.

After failing with his first serve Tsonga gave his opponent a taste of his own medicine, however - pulling him out of position with a setup shot before unloading a smash to keep his hopes alive.

Those hopes looked set to be dashed for good just minutes later, as Federer immediately gave himself a break opportunity (thanks partly to a fortuitous line call) that would almost certainly have signalled the end of the contest. But Tsonga once again showed his mettle, rifling a forehand past Federer as a high-risk strategy paid off.

It was a strategy that he would keep with in the ensuing tiebreak, although he did not initially reap the same rewards as Federer created a first championship point at 5-6 with a pinpoint ace down the middle. It was somewhat ironic, then, that Tsonga would save it on his second serve - trying to batter Federer into submission with another forehand before finishing the job with an identical stroke as the ball limped back over the net to him.

From there Federer seemed to sense the contest was always destined for a decider, as Tsonga reeled off an ace of his own and then yet another forehand to bring about a third set.

As both players recovered from the exertions at the end of the second stanza the third set went with serve without too much fuss, before Federer once again turned up the temperature with the contest reaching a critical point at 4-3, with Tsonga once again serving to remain on level terms.

Two break point opportunities were swatted away by the Frenchman - one after a serve-and-volley sequence and the other after an acrobatic dive - but Federer got lucky at the third time of asking, screaming with delight when he saw his opponent's limp forehand drift out.

From there it would be unfair to suggest Tsonga gave up the chase, but Federer certainly made light work of the finish, winning the first three points of his service game to give him three championship points a full 40 minutes after he had wasted his first.

This time there would be no mistake, as another neutered Tsonga forehand allowed Federer to smash an unreturnable overhead volley - bringing with it a victory to end his 2011 season in a positive fashion.

"Thanks to my team, my family, the sponsors, all the fans, you're amazing, see you next year," the 30-year-old concluded.