Chris Froome stormed into the lead of the Giro d'Italia with a stunning solo ride as Simon Yates' hopes of glory were demolished on the biggest mountain of the race.
Team Sky's Froome attacked with 80 kilometres of the demanding 181km stage from Venaria Reale to Bardonecchia left and won the stage by two minutes and 59 seconds from Movistar's Richard Carapaz.
The Briton takes the race leader's pink jersey as defending champion Tom Dumoulin came home fifth, three minutes and 23 seconds down.
Froome, who began the day fourth in the general classification, three minutes and 22 seconds off pink, now leads by 40 seconds from Dumoulin.
Yates, who began the day with an advantage of 28 seconds over defending champion Dumoulin, had cracked on the Colle delle Finestre, finally crossing its gravel-road summit more than 15 minutes after Froome.
Froome is bidding to hold all three Grand Tour titles at the same time, following on from his fourth Tour de France crown and La Vuelta win last season, racing despite his ongoing battle surrounding a positive test for Salbutamol at the end of La Vuelta.
And after all his struggles in the first two weeks, which had left him almost five minutes off pink at one stage, this was an astonishing ride as he replaced his fellow Brit at the top of the standings.
After Mitchelton-Scott's Yates began to struggle as soon as the riders hit the Finestre at the mid-point of the stage, Froome attacked five kilometres from the summit as the roads turned to gravel.
Having crested the summit some 41 seconds ahead of a five-man group including Dumoulin, his gap only continued to increase on the descent and then over the climb of the Sestriere.
He began the final climb to Bardonecchia with a lead of almost three and a half minutes and continued to pace his way up as a group including Dumoulin and Frenchman Thibaut Pinot (Groupama-FDJ) struggled to make an impact.