The Team Sky rider triumphed by three minutes on the rest of the field to move 40 seconds ahead of Dutchman Tom Dumoulin overall.

He is bidding to become just the third man to hold the Giro, Tour de France and Vuelta a Espana titles at the same time.

Fellow Briton Simon Yates cracked spectacularly elsewhere today to cross the line almost 39 minutes behind Froome and tumble out of contention down to 18th overall.

Froome, who is seeking to clear his name after failing a drugs test for having double the permitted levels of asthma drug salbutamol in a sample given during the Vuelta last year, cut a controversial figure on the entry lists and struggled throughout the first-half of the three week race.

But a stage win last week followed by a strong time trial kept his podium chances alive and he showed attacking intent by breaking clear 100km into the 181 stage from Venaria Reale to Bardonecchia.

Yates had already been dropped by the time Froome made his move and it was left to Dumoulin to take up the chase.

Froome, who was chased by a man carrying a giant inhaler during one climb in a sign of the anti-doping distractions, ruthlessly pressed home his advantage to cross in 5 hours 12min 26sec.

Richard Carapaz of Ecuador and Movistar was second, three minutes down, with Thibaut Pinot of France and Groupama-FDJ crossed third another seven seconds back.

Dumoulin crossed fifth, 3:23 behind Froome.

Pinot moved into third overall, 4:17 down as Domenico Pozzovivo of Italy and Bahrain-Merida fell from third to sixth.

A 214km mountain stage from Susa, Piedmont to Cervinia is scheduled for tomorrow before a processional finale in Rome on Sunday (May 27).