France made it a 1-2 as Pierre Rolland (Europcar) crossed the line around a half a minute further back to take second.
Ag2r La Mondiale rider Bardet attacked the remnants of the day’s main break just before the summit of the Hors Category Col du Glandon with 40 kilometres to go, chiselled out an advantage of around 40 seconds on the descent and held on to the finish in St Jean de Maurienne.
It was a stunning effort from a man who finished sixth overall last year and was made all the impressive by the fact he had to get over the picturesque Lacets de Montvernier climb with 10 kilometres to go and hold off a flying Rolland as well as a half dozen others.
“It was a crazy stage,” Bardet said afterwards.
“We attacked right at the start. I had quite a lot of chances with [teammate] Christophe Riblon in the break with me. I knew I just had to get a gap, and everyone was really tired. I can’t believe it.
“To start, getting the breakaway was really hard. It was a fast pace but it was tough to get involved in it. I wanted the victory, so I just had to go through that pain. It’s been amazing, phenomenal, the crowds… it was like being in a football stadium, there was that much noise generated. I felt really supported today.”
The original break has a whopping 28 men in it, including Ireland’s Dan Martin and even though he imposed himself as best he could, making the front group when the break split, he was later distanced and crossed the line over 17 minutes behind.
While Bardet et al were duking it out up front, the battle for the yellow jersey was no less intense behind as Chris Froome once again resisted the best of what his challengers could throw at him.
Alberto Contador (Tinkoff Saxo) might be over six minutes down overall but he showed he’s still willing to fight by attacking on the Glandon and going clear of the yellow-jersey group.
Defending champion Vincenzo Nibali also lit things up with a sally of his own near the top of the climb and while Froome’s group thinned out significantly, the race leader himself proved unshakable and they caught Contador on the descent.
Nibali went again on the final climb but Quintana, who stands the most realistic chance of overhauling Froome, was rather quiet for a man who promised to take the yellow jersey from Froome in the Alps.
That group of contenders finished in a stalemate but with gruelling summit finishes at La Toussuire and Alpe d’Huez to come today and tomorrow, perhaps the Colombian will wait until then to claw back the 3:10 he needs to be champion in Paris on Sunday.
Afterwards, Froome said only Quintana and Valverde can usurp him of yellow “I always had team-mates with me today and they all rode really well.
“That makes my job a lot easier – when they’re so strong like that. We always had the situation under control.
“We’re getting towards the end now, with two short mountain stages left, but it’s still going to be hard. I’m in good shape and happy with how I’m feeling.
“I was struggling a bit at this point two years ago whereas this time around I’m much more confident. I’ve only got Nairo Quintana and Alejandro Valverde to really look out for now.”