Roger Federer became the most successful player in season-end championship history with victory over Jo-Wilfried Tsonga to win the ATP World Tour Finals.
Federer marked the 100th final of his career with his 70th title and an unprecedented sixth at this event, winning 6-3 6-7 (6-8) 6-3 in two hours and 18 minutes.
A set and a break up, the Swiss legend almost had his hands on the trophy - only for Tsonga to hit back and save a match point to dramatically force a decider.
But the 16-time Grand Slam champion showed all his class and experience to retain the title in front of a 17,500 capacity crowd at London's O2 Arena.
The 30-year-old becomes the oldest player to lift the trophy, joins Ivan Lendl on an unmatched 39 match wins at this tournament and replaces Britain's Andy Murray as world number three.
"I couldn't be more happy, I couldn't be more exhausted," said Federer who ended a campaign without a Grand Slam title for the first time since 2002.
"Jo sapped every last bit of energy out of me. There couldn't be a better way for me to finish the season.
"I really enjoyed every minute of being here, see you next year."
Federer had won seven of their 10 previous meetings - including all three indoors after victories in the recent Paris Masters final and the opening match of the competition last Sunday.
But their most memorable encounter came in the quarter-finals of Wimbledon this year, when Tsonga came from two sets down to clinch a stunning triumph on Centre Court.
The Frenchman said beating Federer here would mean more because of the silverware at stake and that he would be prepared to "break my two ankles" to do so.
He got off to an assured start, marking his first delivery of the match with a huge ace and dropping only one point on serve while putting Federer under plenty of pressure.
But the worst position Federer faced was deuce as his plan of outmanoeuvring the big-hitting sixth seed came to fruition, and in game eight he pounced.
Two thumping backhands gave him 0-30 before he sent the crowd wild by passing Tsonga up the line to register three break points. The first was taken when Tsonga netted a forehand volley.
Federer converted his third set point to assume a commanding position, and there would be no let-up for a dejected Tsonga, who repeatedly shaped to smash his racquet before pulling away.
He came through a sticky position in game three of the second set, but that proved a warning for worse to come and Federer unleashed a stunning forehand winner to strike for 3-2.
Tsonga faced another break point in game seven but he managed to save it and that would prove crucial as Federer, serving for the match at 5-4, capitulated.
Out of nowhere, Tsonga was back in contention - pumping his fists, roaring with delight - and the spectators toasted the possibility of seeing a deciding set.
A tie-break beckoned and Federer crafted his way to 5-2 before reeling off an ace for 6-5. The trophy presentation party were already waiting courtside, but Tsonga was going nowhere.
He wrong-footed Federer with a forehand on match point, sent down a booming serve for set point and took it with a vicious forehand that landed at Federer's feet.
Both men gave everything they could to wear the other down in the deciding set, but it was Federer who always seemed the more capable.
He cranked up the intensity in game seven to break for 5-3 - Tsonga failing to control a forehand on break point number three - and let out an ear-piercingly joyous scream.
When Federer served out to love with a smash, it was time to party.
"Congratulations, Roger," said Tsonga. "Without you, I can maybe get some other titles. But you are here, you are the best. It's amazing to play on this court and be in London."