Simon Yates has one more mountain test to pass in his bid for La Vuelta victory after stretching his lead by more than a minute with a superb ride on stage 19 to Andorra.
The Bury rider finished second to Frenchman Thibaut Pinot on the Coll de la Rabassa, but successfully distanced his main rival Alejandro Valverde by over a minute.
Yates leads Movistar's Valverde by one minutes 38 seconds, with LottoNL-Jumbo's Steven Kruijswijk a further 20 seconds back in third, ahead of Saturday's short, punchy stage 20 to a summit finish on the Coll de la Gallina in Santuario de Canolich.
Yates, 26, is seeking his first Grand Tour victory, and what would be a fifth consecutive Grand Tour win for a British rider following Chris Froome's Tour-Vuelta-Giro treble and Geraint Thomas' Tour de France victory in July.
And the Mitchelton-Scott rider took a major step towards achieving it on a day where he comfortably looked the strongest of the contenders, taking 67 seconds out of Valverde on the road and a further six seconds in bonuses.
"I felt good," Yates said. "I felt good myself when I tried. The team did a fantastic job again.
"Jack (Haig) did a really good job to set me up before I went away, and Adam (Yates) was always behind in case I came back, so we did a fantastic job, but like I say, we're focused on tomorrow now.
"I have to thank Thibaut for helping me. He could have easily sat on. Of course, he wanted the stage, but he could have stayed behind and not helped, but he helped, so chapeau. You don't forget things like that very fast."
Yates beat Valverde by 67 seconds on the road and picked up another six seconds in bonuses for second place.
It was a second stage win for Groupama-FDJ's Pinot following his success on stage 15, but all eyes were on the fight between Yates and Valverde.
Movistar made the first move, sending Nairo Quintana up the road early on the 17km final climb to try to tempt Yates out.
Kruijswijk and his team-mate George Bennett quickly responded but Yates initially sat in.
Yates, who makes Andorra his home these days and knows the roads well, did not budge when Pinot attacked 11km from the summit but then made his own move to join the front group with 10km left, and Valverde had no answer.
Quintana dropped back for his team-mate but their chase began to fall apart when the Colombian suffered a puncture, while Yates continued to drive the pace at the front.
The gap quickly grew and it was clear Valverde had no response as the likes of Wilco Kelderman and then Rigoberto Uran left him behind.
Yates was happy to let Pinot take stage honours, knowing he has put himself in the box seat to effectively secure victory on Saturday before Sunday's processional stage into Madrid.
"I'm very wary of tomorrow," Yates added. "It's exactly what you just said to me now about what could happen in one day, so I'll try to stay focused now and of course enjoy the day, but really it's not over until it's over."
