Geraint Thomas left in disbelief after 'insane' day on Alpe d'Huez at the Tour de France

Geraint Thomas remains in shock after becoming the first Brit to win on the Tour de France's iconic summit finish to Alpe d'Huez, and becoming the first man in history to do so in the leader's yellow jersey.

Thomas now leads the race by a healthy 1-39 margin over Team Sky team-mate Chris Froome and 1-50 over Tom Dumoulin (Team Sunweb) in third.

"Not in my wildest dreams did I ever think that I would win up here," Thomas said. "It will stay with me for the rest of my life. It is just insane.

"Even as I crossed the line, I thought 'surely there is someone still up the road'. Insane, like not even in my wildest dreams did I think I would win at Alpe d'Huez, and to do it in the yellow jersey."

>>> Geraint Thomas takes stunning win in the yellow jersey atop Alpe d'Huez to extend Tour de France lead

Thomas added six seconds to Dumoulin, who placed second, with the bonus seconds added in and four seconds on Froome. He leaves the Alps as the strongest looking favourite and sits just ahead of Froome, who won the Tour de France already four times.

Team Sky have been preparing Thomas for this moment, gradually moving him away from his role as track and one-day racer and turning him into a bona fide stage racer.

That change saw him win the Critérium du Dauphine last month, but he is still largely unproven over three weeks with his best Tour finishes being two 15th places in 2015 and 2016.

"Honestly no [I'm not thinking of the overall win], I just want to enjoy this victory, it's unbelievable. I can't believe it," Thomas said.

"I honestly mean it when I say Froome is still our leader. He knows how to race for three weeks. For me, who knows, anything could happen. I could have a bad day and lose 10 minutes.

"It's a great position for us to be in and hopefully I can enjoy tomorrow because it was hard to enjoy today."

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Tomorrow will also be a chance for Sky to clarify the leadership roles, something that Thomas said on Tuesday would become clearer after the summit finish to Alpe d'Huez. As for Froome, he declined to speak to waiting journalists at the finish line and at the team bus, something that is far from the norm for a man who is used to media attention.

Meanwhile Thomas recognised the "unknown" possibility of keeping the yellow jersey through the third week, having previously cracked or crashed when given the chance of Grand Tour leadership.

"Yeah, I don't know whether I can keep going for three weeks. That's the big unknown. I hope so but I think the big difference from when I was doing a lot of work is that I wasn't thinking of GC then. It's been in the back of my mind this time, I was back-up leader so I didn't do a lot for the first nine days.

"That's the big unknown, the big question mark, and why Froome is still our leader. You know you can rely on him to be consistent. It's a great position for us and gives us a little extra card to play. Time will tell but I just want to enjoy tomorrow."

Wearing the yellow jersey, Thomas first lifted the pace for a Froome attack on the famous Alpe d'Huez climb where Fausto Coppi first won in 1952. Froome attacked with 3.8km remaining, caught Steven Kruijswijk (LottoNL-Jumbo) and kept going.

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Behind, Thomas rode on the coattails of Dumoulin, and after a ceasefire and some more attacks, Thomas sprinted away from the rest in the final 300 metres.

"It was a perfect day," Team Sky sports director Nicolas Portal said. "For G to win on Alpe d'Huez in yellow and drop Nibali, Bardet and those guys – that's a big achievement for him.

"The tactics are the same, we keep the same position. We have more chances to win the Tour with Froomey but with G flying like this, it's perfect. We keep our two cards and day by day we go like this."

Thomas added, "Whatever happens now it will be a successful race and now even more so. Every day in the jersey is a bonus, and we'll just see what happens."

Thomas will be hoping for a less tiring day on Friday on a stage to Valence that looks idle certain to end in a breakaway victory or bunch sprint, before preparing for hilly terrain at the weekend and the mountains of the Pyrenees in the final week.