Sébastien Gros took advantage of a major slip from overnight leader Rory McIlroy to open up a one-shot lead during the third round of the BMW PGA Championship.
World Number Eight McIlroy had opened up a three-shot lead after two rounds of the first Rolex Series event of the season, with enormous crowds following him round at Wentworth Club.
Conditions were windier on day three in Surrey and McIlroy dropped two shots on the front nine compared to Gros' two birdies, leaving the Frenchman one shot ahead at 11 under.
Last season's runner-up Francesco Molinari was then at nine under, one ahead of Finn Mikko Korhonen and England's Lee Westwood.
Life is never dull with Korhonen and he sandwiched an eagle on the fourth with a bogey on the third and a birdie on the sixth.
Once the final group got under way, both McIlroy and Sam Horsfield hit excellent approaches into the first and while the Northern Irishman missed his attempt, Horsfield holed from four feet to cut the lead to two.
McIlroy looked in big trouble when he found trees and sand with his first two shots at the third and despite a beautiful bunker shot, he could not get up and down.
The lead stayed at two, however, with Horsfield also making a bogey after a poor chip.
Gros started his round with three pars but took advantage of the par five fourth and when Horsfield found a ditch off the tee on the same hole for a bogey, the 28 year old was two shots clear of the group in third.
Westwood joined that group in some style as he added to a birdie on the seventh with an eagle on the 12th.
Korhonen had missed good birdie opportunities on the ninth and tenth but he made amends with a gain on the 11th, while Molinari hit a stunning approach to tap-in range on the seventh for a first birdie of the day.
McIlroy got in huge trouble on the sixth, finding trees on the right and failing to advance his second before having to play out and leaving himself a 104-yard up-and-down for bogey. He failed to make it and Gros was in the lead.
A brilliant tee-shot from Westwood on the par three 14th left him just a shot off the lead and when Molinari put a second consecutive approach inside three feet, the group in second had swelled to four.
McIlroy needed a response and he got one on the seventh, holing a 15-footer for a first birdie of the day to go back to the top of the leaderboard.
Westwood missed a short one on the 15th for a first bogey in 42 holes and Korhonen three-putted the 14th, with Horsfield dropping a shot on the eighth after finding nasty stuff off the tee.
While those around him endured a roller coaster, Gros was a picture of consistency and he holed a ten-foot putt on the ninth to turn in 33 and lead on his own.
Marcus Kinhult set the clubhouse target at seven under after a 68 containing a pair of eagles.
The Swede's two-shot gains on the fourth and 12th sandwiched birdies on the seventh and ninth but he dropped shots on the fourth and 17th on the way home.
Horsfield, defending champion Alex Noren, Thai Kiradech Aphibarnrat, South African Darren Fichardt, England's Ross Fisher and countryman Robert Rock were also four shots off the lead.
