Nikolay Davydenko won the biggest title of his career with a 6-3 6-4 victory over US Open champion Juan Martin del Potro in the final of the Barclays ATP World Tour Finals at London's O2 Arena.
The Russian, who beat Roger Federer in the semi-finals on Saturday, went one better than last year having lost to Novak Djokovic in the showpiece 12 months ago.
Del Potro knew victory would take him above Andy Murray - whom he had pipped for a place in the last four by one game - to No.4 in the rankings but he was thoroughly outplayed.
Davydenko picked up where he had left off against the world No.1 while Del Potro, who had played quite brilliantly to beat Robin Soderling on Saturday night, looked nervous and tentative.
The Russian has been talking all week about his new-found love of volleying and he took every opportunity to put pressure on his opponent.
And it paid dividends in the fourth game, Davydenko taking his second break point after the Argentinean - not for the first time in the tournament - had been pulled up for a foot fault.
This was the Del Potro who had started so hesitantly against Murray in his first match. He was given a chance in game seven when Davydenko double-faulted to go break point down but the 28-year-old is not easily rattled and he recovered to hold and move 5-2 ahead.
The Russian really was playing with supreme confidence and he easily served out a set in which he had barely put a foot wrong.
Del Potro needed something special in the second set and two huge forehand winners in Davydenko's first service game hinted at better to come.
But it was the sixth seed who again had the first break points, in game five, although this time Del Potro proved equal to the challenge, firing down two big serves.
The next game brought the same scenario, with the Russian getting himself out of trouble after for once failing to find the lines.
Davydenko had won two of their three previous meetings, most recently in the group stages of the same tournament last year, and he moved to within sight of victory as some superbly constructed points left his opponent facing three break points at 4-4.
The Russian needed only one, and serving for the match he never looked like faltering, clinching victory when Del Potro netted a forehand.
Meanwhile Bob and Mike Bryan picked up their third Barclays ATP World Tour Finals title to ensure they finish the year ranked No.1 in the world.
The American twins, winners in 2003 and 2004, defeated seventh seeds Max Mirnyi and Andy Ram 7-6 (7-5) 6-3 at London's O2 Arena to leapfrog Daniel Nestor and Nenad Zimonjic in the rankings.
Mirnyi and Ram had beaten the Bryans in their first group match but they could not engineer a repeat on Sunday, the Americans securing the only break of serve in the second set.
Bryan and Bryan finish on top of the rankings for the fifth time in the last seven years.