The first stage in the high mountains and first in the Alps, the tenth, was won by Quick-Step Floors rider Julian Alaphilippe, who attacked on his own with to go from a large breakaway group that included race leader Van Avermaet. The aforementioned retained the yellow jersey and extended his lead to 2 min 22 s, when pundits predicted the first day in the Alps would be his last as overall race leader. Alaphilippe also took lead of the mountains classification. Thomas achieved back-to-back wins both from the group of overall contenders on stages eleven and twelve by pushing the breakaway riders until the very end. In the steep summit finish of the eleventh, Thomas attacked in the final , passing lone breakaway rider Mikel Nieve (Mitchelton-Scott) and managed to distance himself from Froome and Dumoulin by twenty seconds to take the win. On the twelfth stage, which was the final day in the Alps, Thomas won the sprint on the flat finish after the climb to Alpe d'Huez. LottoNL-Jumbo's Steven Kruijswijk was caught by the group of overall contenders in the final kilometres after he had launched a solo attack with remaining. Following the stage, the general classification top three was: Thomas in first position, Froome second, 1 min 39 s down, and Dumoulin third, a further 11 seconds behind. General classification contender Vincenzo Nibali, who was fourth overall, was forced to withdraw from the Tour following the stage after an incident near the summit of Alpe d'huez where he fell off his bike fracturing a vertebra taking Roglic down with him. It was initially suspected that the crash had been caused by a police motorcycle driving in front of him, but it later emerged that he became caught in a spectator's camera strap. Nibali's team management saw the lack of crowd control from the police and spectators lighting flares as contributing factors. Following the incident, Christian Prudhomme appealed to fans to show the riders most respect. Many riders left the Tour during the Alpine stages, either being forced to abandon due to fatigue and injury, or were disqualified for finishing outside the cut-off time; riders of note were the sprinters Mark Cavendish, Gaviria, Greipel, Groenewegen, and Kittel.