Coco Gauff was 15 when she announced herself as a future Wimbledon champion, coming through qualifying, beating five-time winner Venus Williams and reaching the fourth round. 

That was seven years ago. Until this week, while she has won grand slams in Paris and New York, the fourth round remained her high-water mark in London.

On Tuesday (local time) she finally booked a semi-final place, defeating fourth-seed Jessica Pegula 4-6 6-3 6-3 to become the highest-ranked woman left in the draw.

She is also, with Naomi Osaka losing to ninth seed Karolina Muchova 7-6 (7-4) 6-4, the only player left to have won a grand slam.

The seventh-seeded Gauff began badly on Centre Court on another baking hot day in south west London. From 40-0 up in the opening game she lost the next five points, including a pair of double-faults. 

After breaking back in the sixth game, Gauff was immediately broken to love with two more double-faults.

Another double-fault followed at the start of the second set but Gauff recovered to hold and then her serve began to fire. Pegula, on her Centre Court debut, was the one to crack and it went to a decider.

Gauff broke early, Pegula responded, but Gauff broke again to take the tie.

"Honestly, it's pretty insane, considering I hadn't won a match on grass in two years before this tournament," Gauff said during her on-court interview.

"It feels really special considering the results I've had of late and just especially on this surface," said the 22-year-old later.

"I'm able to relax a bit because, I feel regardless of how the rest of this tournament goes, I really think I've found a bit of a breakthrough on grass.

"In the past there's commentary on my game, how maybe it doesn't mesh with this surface, things like that," she said.

"I think just trusting myself, trusting that my groundstrokes are good enough to be with anyone on this surface.

"Obviously I'm not satisfied. I want to go all the way."

On No.1 Court, where Osaka last week beat Australia's Daria Kasatkina, the four-time grand slam winner appeared to have serious intent when she reduced her walk-on outfit to just the train.

But after squandering a break chance at 5-5 she made too many errors in the tie-break and went a set down. 

The 14th seed failed to exert much pressure on Muchova's serve in the second set and was broken in the ninth thanks to two double faults and a wild volley.

"I played three times on this court and it was 0-3," Muchova said. "I had a not good relationship with this court, but I am super happy we finally made it and I got the win."

Wednesday's women's quarter-finals feature Marta Kotyuk (Ukraine, 12th seed) against Jasmine Paolini (Italy, 13th), and Linda Noskova (Czech, 9th) playing Elise Mertens (Belgium, 25th).

Whoever comes through will be a debutant winner and if it is Muchova or Noskova they will be the third Czech Wimbledon winner in four years after Marketa Vondrousova and Barbora Krejcikova.