Nikolay Davydenko beat weary Argentine Juan Martin del Potro 6-3, 6-4 to claim the ATP World Tour Finals title at the O2 Arena on Sunday.
The wiry Russian, who has climbed to sixth in the world this week, produced a faultless display to claim the biggest title of his career and a $1.5 million cheque.
Davydenko, 28, broke Del Potro's serve in the fourth game and then pounced again at 4-4 in the second set before serving out for victory in one hour 23 minutes.
"For me it was amazing to come here ranked at seven and to win the tournament, I surprised myself," Davydenko said on court in front of another 17,500 sell-out crowd.
Davydenko's challenge began with defeat last Monday against Novak Djokovic in his opening round-robin match but he recovered with inspired victories over Rafael Nadal, Roger Federer and finally Del Potro, players who between them won all the grand slam prizes on offer this year.
Del Potro, the US Open champion, looked flat throughout the contest and never really got a foothold in the match that Davydenko dictated from start to finish.
Only once did he threaten to make a real match of it, when he created chances to break the Davydenko serve midway through the second set.