Retief Goosen held his nerve to claim his second Lancome Trophy after a rollercoaster final day in at Saint-Nom-La-Bretèche outside Paris.
Goosen saw a five-shot lead reduced to just one on the back nine before seeing off the challenge of Ryder Cup hero Paul McGinley to complete a wire-to-wire victory.
The South African carded a final round 70 for an 18 under par total of 266, four shots ahead of McGinley with England's Ian Poulter sharing third with France's Raphael Jacquelin a shot further back.
Ireland's Damien McGrane finished on nine-under, Padraig Harrington on eight-under, and Gary Murphy on four-under.
It was Goosen's fourth victory in France and the Eur209,000 first prize gives him an outside chance of retaining his title as European number one for a third year, although he still trails Ernie Els.
Goosen began the day three shots ahead and stretched it to five after he birdied the first and playing partner McGinley bogeyed. That left Colsaerts to take up the chase and twice he succeeded in reducing his deficit to two shots.
Firstly he eagled the sixth from 25 feet while Goosen took six, and after the South African birdied the seventh, the young Belgian birdied the eighth. Goosen went three clear again on the ninth when Colsaerts found trouble off the tee, but there was more drama to come at the 11th.
With McGinley sitting just eight feet from the hole, Goosen took two to escape from rough to the right of the fairway to make bogey, while Colsaerts escaped at the first attempt from a similar spot only to find the water at the back of the green.
That led to a double bogey six and after Goosen had missed for par, McGinley calmly holed to close the gap to just one shot. Goosen could be forgiven for thinking back to 2001 when he lost a four-shot lead with four holes to play against Sergio Garcia, but he responded to the threat in style with birdies at the next two holes, the second from a matter of inches, to edge three ahead again.
That proved decisive and Goosen's path to victory was sealed when both McGinley and Colsaerts ran up double bogey sevens on the 16th.