HARRIET DART bet umpire Kelly Rask £50,000 that she was right about a disputed line call during the Nottingham Open.
The tennis star suffered an ill-tempered defeat to British rival Katie Boulter.
During the match, Dart ranted at the official that she was "embarrassing" herself after a disputed line call.
The British number two was convinced that a ball was out by Rask differed in her opinion.
She also later accused Rask of "threatening" her.
Katie Boulter breaks down in tears after winning Wimbledon warm-up tournament
Defending champion Boulter kept out of the drama and sealed a 6-7 (5) 6-4 7-5 victory.
The players are good friends off the court, but Boulter will probably leave Dart alone until she cools off.
Dart, back in the world's top 100, was unhappy with the line judging throughout but first lost her temper midway through the second set.
A ball from Boulter was called out but overruled by Rask and Dart shouted: "The ball is so far out, this is embarrassing, you're embarrassing yourself. You should be embarrassed."
After losing the replayed point she then placed the ball down on the ground and said: "It was here, no joke, everyone here knows it."
CASINO SPECIAL - BEST CASINO WELCOME OFFERS
Rask replied: "Harriet, stop now or you're going to get a code (violation), I've had enough now. That's it."
At the end of the game Dart then asked to see the referee which is when she offered a wager with Rask.
Dart vented at the umpire: "I've got a reason to call the referee, because of the calling, I'd like them to watch. If we watch that back I can promise you, I would back £50,000 that ball is out, I'd shake your hand now. It's a joke how far that was out."
Two games later Dart spoke to referee Jane Harvey and accused Rask of unjustly "threatening" her with a code violation.
Wimbledon fans rally together in queue after security checks sparked 9HOUR wait
It was a sideshow to what as an enthralling contest between the top two British players.
Boulter's star has risen considerably since she won her maiden WTA Tour title here 12 months ago as she added a second, more prestigious title in San Diego and has broken into the world's top 30.
She will be targeting another long run after overcoming a titanic three-hour-and-13-minute battle against Dart.
Earlier, Heather Watson enjoyed her first main tour-level win since February after she beat Kayla Day 4-6 6-0 6-4.