Britain's Fed Cup captain Anne Keothavong is "in awe" of her players after they won promotion to World Group II for the first time in 26 years.
Every match in their 3-1 play-off win over Kazakhstan in London was a nerve-shredding three-setter.
Katie Boulter was a set and break down before the decisive win over Zarina Diyas, and Johanna Konta trailed 4-1 in the third set against Yulia Putintseva.
"It was such an incredible effort," Keothavong said.
"I am just totally in awe of these women."
Boulter's 6-7 (1-7) 6-4 6-1 triggered wild celebrations after Great Britain finally got themselves out of the third tier of women's team tennis after four failures at the same stage in the previous seven years.
Keothavong, who played in two of those play-offs and captained the others, said the victory at the Copper Box Arena was "right up there" as one of her best achievements in tennis.
"I couldn't get there as a player but to be able to captain this achievement and to finally achieve it together after so long is definitely a highlight for me," she said.
"Watching the players develop and grow; watching Jo lead this team as the number one; playing a small part in something much bigger is a very proud moment for me."
Konta, whose stunning 4-6 6-2 7-5 victory over Putintseva on Sunday had put Britain one win away from promotion, said she was "speechless" following the team's triumph.
"I have dreamed of being a part of the team that was able to achieve this," the world number 46 added.
'Springboard for bigger things'
Keothavong hopes Fed Cup success will provide a "springboard for bigger and better things" for 22-year-old Boulter.
The British number two was impressive on her debut at February's Europe/Africa Zone round-robin event in Bath, winning all of her singles rubbers.
She held three match points against Kazakh number one Putintseva on Saturday although she eventually lost, but she picked herself up - despite a back problem - to win the tie with the comeback win over Diyas.
She has shot up the world rankings in the past year and is now ranked 86th after breaking into the top 100 in November.
And in January Boulter, alongside British team-mate Cameron Norrie, beat 23-time Grand Slam champion Serena Williams and Frances Tiafoe in the mixed doubles at the Hopman Cup.
"For Katie, this can be used as a springboard for bigger and better things. The players need to use it in a positive way," Keothavong said.
Boulter said she will learn from the experience, especially the defeat by Putintseva that she said at the time would stay in her mind "for a long time".
"We all have good days and bad days but I will fight and get up for the next match no matter what the circumstances are," Boulter said.
'Utterly brilliant', 'inspired', 'an amazing achievement' - reaction to the GB's success
Former British number one Annabel Croft, now a television commentator and analyst: "Absolutely amazing weekend of tennis. Congrats to Johanna Konta, Katie Boulter, Anne Keothavong and the rest of the Fed Cup team. Inspired performances with home fans cheering at the Copper Box.
British doubles player Jamie Murray, who helped the nation win the Davis Cup in 2015: "What a weekend for the GB Fed Cup team! Amazing achievement girls!"
Leon Smith, Britain's Davis Cup captain: "That was utterly brilliant from our GB Fed Cup Team. This team deserves so much praise. Well done all. Bring on the World Group! Come on!!"