Great Britain will play at Fed Cup's top table for the first time in 26 years after Johanna Konta and Katie Boulter both produced comebacks to secure a 3-1 victory over Kazakhstan.
The play-off was tied at 1-1 overnight at London's Copper Box after Boulter was unable to take three match points in a heartbreaking defeat to Kazakh number one Yulia Putintseva on Saturday evening.
The visitors looked set to take a 2-1 lead when Putintseva led Konta by 4-1 and two breaks of serve in the deciding set of yesterday's first rubber, only for the British number one to win the last four games in a 4-6 6-2 7-5 victory.
It was Konta's 11th singles success in a row in the competition and meant victory for Boulter against Zarina Diyas would at last get Britain over a hurdle they have fallen at in four of the last seven years.
Boulter was swiftly enveloped in a group hug as the whole British team celebrated on court.
She said in her on-court interview: "I was just coming out here trying to get one win for the team. Johanna did such a great job. I'm so proud of these girls for what they've done and I just wanted to make them proud today.
"I think I showed yesterday how much it means to me. I was so close but I just couldn't get over the line. I was so nervous but I came back and I'm just so happy."
Captain Anne Keothavong added: "Amazing, just a heroic effort from the players this weekend. Some fantastic tennis. This has been an unforgettable weekend.
Meanwhile, Fabio Fognini became the first Italian to win an ATP Masters 1000 title with a straight-sets victory over Dusan Lajovic in Monte Carlo yesterday.
The 31-year-old followed up his win against Rafael Nadal with a 6-3 6-4 success on the red clay at the Rolex Monte-Carlo Masters.
Fognini had two breaks of serve to Lajovic's one in either set as he rounded off a memorable week in the principality, which also included victories against top-10 seeds Alexander Zverev and Borna Coric.