There is no room for national sentiment on the world's biggest bike race: just ask Australian Cadel Evans.

On the first day in the high mountains of the 100th Tour de France, the 2011 champion virtually lost all hope of winning a second yellow jersey as Britain's Chris Froome stamped his authority on the race.

Froome, last year's runner-up to Sky teammate Bradley Wiggins, capped an audacious solo attack 5km from the summit of Ax-Trois-Domaines with a victory that gave him the race lead and a significant advantage over his rivals.

Spain's two-time winner Alberto Contador finished 1min 45sec off the pace and is now seventh overall at 1:51 behind Froome.

However, the biggest blow was suffered by Evans, who came over the finish 26th at 4:13 behind Froome to drop to 23rd overall at 4:36.

Evans admitted Sky's "really consistent" pace on the arduous 15km slog to the summit of the Pailheres mountain pass left him short for the ensuing 7.8km trek to the finish on the next climb, where Australian compatriot Richie Porte played a decisive role for Sky.

"When you're in the running for GC (general classification), seven kilometres is not a climb that you would normally get dropped on, but on the last climb I had a few problems to get into the mix," said Evans.

"I couldn't even push myself to my maximum and at that point, when you see 20 guys riding away from you, you know you're a long way off the pace."

Given that Evans, 36, came into the race hoping he could provide a stiff challenge to the 28-year-old Froome, stage eight proved a monumental setback.

Arguably the biggest damage was done by Porte, the Paris-Nice winner who on this race will be key for Froome's victory hopes.

Porte is part of Sky's pace-setting squadron on the climbs and typically provides the last wheel for Froome to follow, before the Kenyan-born Briton launches his own solo attack.

Having taken over from Englishman Peter Kennaugh early on the 7.8km climb to Ax-Trois-Domaines, Porte put the hammer down so efficiently that earlier escapees Nairo Quintana and Pierre Rolland were soon reeled in.

The Tasmanian's pace claimed bigger victims, though, in Contador and Evans.

"Richie Porte and Pete Kennaugh did some incredible work," said Froome.

Porte affirmed: "I've come to the Tour with the best form of my career."

Sky are now firmly in control, perhaps much earlier than anyone had expected, and Porte added: "We're not going to be complacent, we've got a long long way to go and there's some hard stages. But looking at it today, he's (Froome) looking good."

The prospect of yet another 1-2 for Sky, following the Wiggins-Froome 1-2 on the 2012 podium, is now looking a distinct possibility.

But as Froome bids to become the second Briton and the first African-born rider to win the race, he will do so with the cloud of suspicion hovering.

His and Sky's performance prompted comparisons with those of US Postal, the team once led by disgraced American Lance Armstrong, who has been stripped of all seven of his race victories after admitting to doping throughout his career.

Armstrong's trademark was to put his team on the front, set a searing pace which fatigued rivals, and launch solo attacks to claim stage wins and yellow jerseys.

Froome, however, insisted he is racing "100 per cent" clean.

"It's the unfortunate position we find ourselves in at the moment. Eyebrows are going to be raised, questions are going to be raised about our performances.

"But I know the sport has changed. There is absolutely no way that I would be able to get these results if it hadn't changed.

"For me, it is a bit of a personal mission to show that the sport has changed. I certainly know that the results I'm getting are not going to be stripped in 10, 20 years time."