Andre Greipel claimed a third victory of the Tour de France with a stage 13 success to Le Cap d'Agde.
Yellow jersey Bradley Wiggins led Team Sky colleague Edvald Boasson Hagen into the finishing straight of the 217-kilometre route from Saint-Paul-Trois-Chateaux, but Greipel (Lotto-Belisol) burst from behind the Norwegian's wheel to triumph.
It was his third stage success after wins on stages four and five, equalling Peter Sagan's haul of triumphs. Sagan (Liquigas-Cannondale) was second, with Boasson Hagen third.
The win, two weeks prior to the London 2012 Olympic road race, showed Greipel will be a major threat to world champion Mark Cavendish's bid for gold on the opening day of the Games on July 28.
With Team Sky's priority Wiggins' bid to win the Tour and with Chris Froome a place behind in second overall, Cavendish has had limited support in his sixth Tour and was cast adrift on the 1.6km Mont Saint-Clair, a brutal short, sharp category three ascent rising out of the coastal town of Sete.
Wiggins retained a lead of two minutes five seconds from Froome, with Vincenzo Nibali (Liquigas-Cannondale) 2mins 23secs behind in third and Cadel Evans (BMC Racing) fourth, 3:19 adrift.
The Tour enters the Pyrenees on the 191km 14th stage from Limoux to Foix, which features two category one climbs, but is likely to favour a breakaway.
Five Frenchman were in the eight-man Bastille Day escape. The best-placed overall was Maxime Bouet (Ag2r La Mondiale), who began the day in 54th place, more than an hour behind Wiggins.
Michael Morkov (Saxo Bank-Tinkoff) attacked alone 60km from home. The Dane was attempting to mark the fifth anniversary of his father's death with victory and increased his lead over his escape colleagues to 1:10 with 40km to go, with the peloton 3:15 behind.
BMC Racing took to the front as the winds threatened havoc and there was a split in the peloton, but none of the overall hopefuls were affected.
Another obstacle was Mont Saint-Clair.
Morkov reached the lower ramps with less than a minute's lead over Wiggins' yellow jersey group and was swamped by the peloton as Evans forged forward with Wiggins, Jurgen van den Broeck (Lotto-Belisol) and Nibali in pursuit.
Froome was behind the maillot jaune, while Cavendish was dropped early on.
Van den Broeck was first over the summit, 23km from the finish, to begin the steep and narrow descent.
The bunch reformed at the start of the run-in along the coast, with Team Sky's Michael Rogers and Froome at the front and a group of stragglers, including Cavendish, more than a minute behind.
Alexandre Vinokourov (Astana) attacked off the front and Michael Albasini (Orica-GreenEdge) followed.
With 8km to go, the peloton were 10 seconds behind the duo and the Cavendish group more than three minutes adrift and out of contention.
Lotto-Belisol, riding for Greipel, were leading the pursuit into the final 5km, with Sagan on the German's wheel.
There was a further split in the peloton inside the final 4km, with Wiggins and his Team Sky colleagues present in the front group, as Vinokourov and Albasini were caught with 2.6km to go.
The gap in the peloton was closed as counter attacks began, with Luis-Leon Sanchez (Rabobank) making a late acceleration.
Wiggins led the pursuit and overtook Sanchez in the finale in his attempt to set up Boasson Hagen.
But Greipel powered to another triumph as the top of the general classification remained unchanged.
In retaining the yellow jersey he won last Saturday, Wiggins is tomorrow set to become the Briton with the most time in the maillot jaune, beating Chris Boardman's record of six days.