Bardet fell down the general classification on the first big mountain stage to La Pierre-Saint-Martin, where Froome won the stage and built on his race lead. The next day, Bardet suffered in the heat and lost more to Froome and other overall contenders.
The stage win made up for it, and Bardet did it with style going solo down the Col du Glandon and up the Lacets de Montvernier.
>>> Five talking points from stage 18 of the Tour de France
"It's big," said the 24-year-old in the brown and white colours of French team Ag2r La Mondiale
"I'm really happy, there's a lot of emotion, I don't realise it yet. I had some bad days in the Tour, so I'm really happy with this win."
At the top of the Col du Glandon, 1924 metres up in the Alps, Bardet left the last of a 29-man escape. Like he did to win the Pra Loup stage in the Critérium du Dauphiné, he bombed downhill solo and continued up the final climb. After the Lacets, with a 45-second lead, he had the last 10 kilometres to Saint Jean de Maurienne to soak in the moment.
"I was close before, we made a tactical mistake in Mende," he added.
"To lose the stage [to Steve Cummings] made me frustrated. Being angry probably helped me win today."
Bardet placed sixth overall in the 2014 Tour behind winner Vincenzo Nibali (Astana). Frenchmen Jean-Christophe Peraud (Ag2r La Mondiale) and Thibaut Pinot (FDJ) placed second and third, respectively.
Much was made of Bardet coming into the 2015 edition. He said that he hoped for a top five, or at least place in the top 10 when the race pulls into Paris on July 26. He now sits 10th overall, but said that stage wins will do for this 2015 Tour.
“I'm surprised to be in the top 10 now. I'm afraid that tomorrow will be a hard day,” Bardet said.
“Last year was extraordinary for us, we also had strange circumstances. To excel, means to perform in 21 stages. I prefer to stay a stage hunter for now. It’s still too early for me, but I'd like to come back and race for GC again.”
Video: Tour de France 2015 stage 18 highlights
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