Katie Boulter stayed on course for a third consecutive Nottingham Open title by defeating Sonay Kartal in an all-British showdown on Thursday.
British No 2 Boulter battled back from a break down in the third set to win a rollercoaster match 6-4 1-6 7-5 in two hours and 26 minutes.
Boulter, who was replaced this week as British number one by Emma Raducanu, won her maiden WTA Tour title in Nottingham two years ago and backed it up last summer.
She trailed 4-2 in the deciding set and had to save a break point to avoid going a double break behind, with the eighth seed struggling in the heat and consulting the doctor.
“I have so much respect for Sonay, she is such a tough competitor and I also know she’s never going to give me anything at any point,” said Boulter.
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“I know she’s going to surpass me at some point, she’s got the game for it, she’s got the head for it. I’m going to have to face that fact.
“But at the very end I just wanted to grit my teeth as hard as I possibly could and get myself over the line. I’m really pleased with myself today. It wasn’t easy, for sure.
“I feel like I step into my house when I come onto this court. I have such great vibes here but the heat was killing me today.
“I am definitely proper British because I can’t handle the heat at all. I’m just glad I got over the line.”
Next up for Boulter is a quarter-final clash against American McCartney Kessler, who raced past Lin Zhu with a 6-1 6-4 victory.
Meanwhile, British teenager Mimi Xu exited in the second round 7-5 6-1 despite a spirited performance against world No 31 Magda Linette.
The 17-year-old, who will make her Wimbledon debut later this month after being given a wild card, won her first WTA Tour match in the first round before sitting an A level biology exam on Wednesday.