LONDON (Dispatches) - Britain's Chris Froome has taken a big step towards winning a fourth Tour de France - and third in succession - as French rider Warren Barguil won stage 18.
Froome reached the Col d'Izoard summit in fourth, just behind Romain Bardet, who is now 23 seconds adrift of the Team Sky man in second place overall.
Barguil, who will finish the race as King of the Mountains, pulled away from Darwin Atapuma to win his second stage.
Britain's Simon Yates still leads the best young rider classification.
Colombia's Rigoberto Uran lost two seconds on the line and is now third overall, six seconds adrift of Bardet.
There are just three stages remaining - two flat routes and Saturday's time trial in Marseille, where Froome is expected to extend his advantage.
The final day in the mountains represented the last realistic opportunity for Bardet, who rides for AG2R La Mondiale, and Cannondale-Drapac's Uran to prevent defending champion Froome claiming his fourth title.
The Briton's struggles on the steep finale in Peyragudes on stage 12 may have given them hope they could inflict similar damage on the punishing Izoard, but Froome's impressive form since that wobble held.
AG2R tried to weaken the group of favorites by taking over from Sky at the front of the peloton over the penultimate climb of the day - the category one Col de Vars - but their tactic only resulted in a stalemate.
The French team drove again on the 14.1km-long climb of the Izoard, putting several Sky riders into difficulty, only for the imperious Michal Kwiatkowski to bury himself in support of Froome and set up Mikel Landa to attack.
Froome refused to chase his Spanish team-mate, who overtook a struggling Fabio Aru to go fourth overall, forcing Bardet to respond, before bridging to the Frenchman and launching an attack of his own.
A burst from Uran towed Bardet back up to Froome but by then the contenders had run out of road to take both the yellow jersey and the buffer they needed for Saturday's time trial.
Froome may be wary of Uran - a solid time trialist who looks stronger as the race goes on - and will not be complacent in negotiating the last three stages, but a fourth Tour title beckons.