Brailsford has given his role to Australian Richie Porte, hailing the Tasmanian as a "Grand Tour winner of the future" but has courted further controversy by leaving out young British stars Peter Kennaugh and Ben Swift, who finished first and second at their national championship last weekend.

With Swift omitted it will leave Team Sky without a recognized sprinter, the riders designated to contest the bunch finishes at the end of predominantly flat stages.

Despite its recent dominance of cycling at the Tour de France and in the Olympics, Britain will only have four competitors in this year's race, but in Froome and sprint king Mark Cavendish (Omega Pharma-Quick Step) it has two jewels in the crown.

Cavendish, who has used his finishing speed to win 25 Tour de France stages, will be hoping his teammates can help him don the yellow jersey after the first stage which finishes in his mother's home town of Harrogate.

Last year's green jersey winner Peter Sagan of Slovakia and Germans Andre Greipel and Marcel Kittel will be his main challengers in these finishes -- with all looking to win the coveted final stage on the Champs Elysees in the French capital.

But the fastest men on two wheels are not contenders for the overall crown, usually losing time on the mountain stages and the individual time trials which decide that ultimate honor.

Froome has proved his worth in both those disciplines, winning the 2013 Tour by over four minutes from Nairo Quintana of the Movistar team.

Colombian Quintana won the Giro d'Italia earlier this year, but has decided against a tilt at the Tour, leaving two-time winner Alberto Contador as the likely main challenger to Froome.

Contador courted controversy after a positive drugs test which annulled his 2010 Tour triumph and the Spaniard has struggled to repeat his earlier victories since serving his ban, but impressive performances in 2014 serve notice of his abilities.

The 31-year-old always protested his innocence after failing a doping control for the banned stimulant Clenbuterol, but his presence as a podium contender will act as a constant reminder that cycling is still struggling to shrug off the doping controversies which have continually haunted the sport.

On the eve of the tour came the revelation that Daryl Impey, the first South African to wear the yellow jersey last year, had tested positive back in February after his national championships for a banned substance Probenecid.

He was withdrawn from the race by his Orica-Green EDGE team while Froome, who has known Impey since his time in school in South Africa, said that the news was a "big shock to me."

Tour de France organizers will be hoping this year's event passes off without a further doping story, preferring the positive images of massive crowds lining the route in both Britain and France to cheer on their heroes rather than the darker side of the sport.