Dan Evans and Kyle Edmund secured huge singles wins to send Great Britain into the Davis Cup semi-finals where they will face hosts Spain at Madrid's Caja Magica.
Edmund gave Britain the perfect start with a 6-3 7-5 victory over Philipp Kohlschreiber, producing another superb performance after Thursday's victory over Mikhail Kukushkin.
That set the stage for British No 1 Evans, who kept his place ahead of Andy Murray, despite his losses to lower-ranked players this week, but he produced a magnificent performance to defeat German No 1 Jan-Lennard Struff 7-6 (8-6) 3-6 7-6 (6-2).
The only disappointment was the size of the crowd, which appeared noticeably smaller than for Britain's two group matches.
The British fans who had stayed made a good noise, though, and Edmund said: "It feels like a home tie playing in Madrid. We really appreciate the efforts to come out here."
Evans' place had been in question but Leon Smith stuck with him ahead of Andy Murray, who was again left out of the side, cheering on from the sidelines, and the captain was rewarded with a display of real skill and heart from the 29-year-old.
He dominated the deciding tie-break and, when Struff's final shot flew wide, Evans leapt high and threw his racket into the air before running to celebrate with Smith and the rest of the team.
It looked like it might again slip away from Evans when world No 35 Struff battled back after losing the first set, but Evans withstood pressure at the start of the third and dominated the deciding tie-break.
When Struff's final shot flew wide, Evans leapt high and threw his racket into the air before running to celebrate with captain Smith and the rest of the team.
The 2015 champions will face host nation Spain on Saturday evening after they knocked out Argentina 2-1.
This victory, though, means they are guaranteed to be back in Madrid next year, with semi-finalists exempted from March's play-off round.
Serbia and Djokovic knocked out
Novak Djokovic's Serbia are out of the competition after a dramatic quarter-final loss to Russia.
The world No 2 levelled the tie with an impressive 6-3 6-3 victory over Karen Khachanov in singles after Andrey Rublev had thumped Filip Krajinovic 6-1 6-2.
With the tie coming down to a deciding doubles rubber, Djokovic was subbed in to partner Viktor Troicki against Khachanov and Rublev, but it was the Russians who came out on top 6-4 4-6 7-6 (10-8).
Serbia had three match points but could not take any of them, with Troicki scooping a horrible volley long on the third one, and Russia made them pay to reach the last four for the first time since 2008.
A distraught Troicki, who won the deciding rubber in the 2010 final, blamed himself, saying: "I probably feel the worst ever.
"I never experienced such a moment in my career, in my life. And I let my team down, and I apologise to them. We had chances to finish it. We didn't do it. I messed up in the crucial moments.
"God gave me once to be the hero, to win the Davis Cup in the deciding rubber. Now he took it away. I'm really, really disappointed in myself that I couldn't hold my focus till the end and finish."
Khachanov and Rublev have been playing as a two-man team following the late withdrawal through fatigue of US Open finalist Daniil Medvedev.
They collapsed to the court in each other's arms at the moment of victory and will take on Canada on Saturday for a place in the final.
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