The Queen congratulated Emma Raducano after the 18-year-old won the US Open with a stunning victory in New York.
Radocano beat teammate Leila Fernandez 6-4 6-3 to end Britain’s 44-year wait for the women’s Grand Slam singles title.
“I congratulate you on your success,” said the Queen.
“It’s an amazing achievement at such a young age, and a testament to your hard work and dedication.”
“I have no doubt that your outstanding performance and that of your opponent, Leila Fernandez, will inspire the next generation of tennis players,” the monarch added in a statement.
British Prime Minister Boris Johnson tweeted: “What a thrilling match! Big congratulations to Emma Raducano.
“You have shown extraordinary skill, poise and courage and we are all very proud of you.”
It was a historic night for the newest British sports star, leading critics to anticipate big things and seemingly put the UK into a standstill…
“A Star Is Born”, “The World’s First Future” – Praise be to Raducanu
Virginia Wade, who was in Arthur Ashe Stadium to witness Raducano’s victory, was the last British woman to win a Grand Slam singles title – at Wimbledon in 1977.
In an unprecedented race, Raducanu became the first eligible player to win a major tournament and did so without dropping a set.
“A star is born,” said tennis legend Martina Navratilova. “Emma Raducano is making history and she’s just getting started.”
Former British top seed Greg Rusedsky, speaking to Amazon Prime, added: “She will be the winner of several major championships, and the world number one ranked.
“It’s the real deal and it’s a breath of fresh air after an 18-year-old won the event.”
Radocano, whose fourth-round run at Wimbledon earlier this summer was her only other Grand Slam appearance, will take home £1.8m in prize money and rise from 150th to 23rd in the world rankings.
Former Wimbledon champion Pat Cash described her success as “amazing”.
“This is amazing [a qualifier winning a Grand Slam] The Australian told BBC Radio 5 Live.
“I think I’m going to wake up. It’s unbelievable. It’s amazing to see this performance.”
“You’re going to win more of these,” said Tim Henman, another former British number one who was on the ballpark in his role at Amazon. [Grand Slams], It’s good.
“This isn’t some flash in the pan or fairy tales. She plays ‘top five tennis.'”
“Her world will be turned upside down but there are good people around her and it will be hell if she can stay injury-free.”
“MOTD delay!” And skillfully checking the results at weddings – Raducanu takes over the UK
Radocano won the title with an elegant performance in a heavyweight match against Canada’s Fernandez that lasted nearly two hours.
By the end, it looks as if the UK has taken control, with many people tweeting to demand that today’s match be postponed.
Presenter Gary Lineker tweeted: “For the first time in my life I’ve tweeted on air, but oh my God, what a performance, what a victory, what an amazing young woman.”
Throughout the match, BBC Sport also received countless messages from fans watching the event with concern.
One of the letters said, “I’m currently at a wedding, checking the outcome. Come on EMMA!! From everyone at Will & Josie’s wedding.”
Mane added in Manchester: “I’m currently at a wedding not skilfully checking the outcome. Sorry Chloe. Come to Emma.”
Ben said in London, “We’re all at Laura and George’s wedding – don’t stop me now! You can’t check the score! Come to Raducanu!!!”