Serme, the 27-year-old European champion, had already produced some stunning performances this week in Philadelphia, including beating world number two Laura Massaro from England and home favourite Amanda Sobhy.

That culminated in overcoming current world champion El Sherbini today in the showpiece match of the tournament.

In only Serme's third ever PSA World Series final, neither player could be separated early on as they shared the opening two games.

It was Serme, however, who came through a crucial third game, coming from 3-0 down to take it in a tense tie-break courtesy of some sublime drop shot winners.

Continuing to play with precision and accuracy, Serme managed to come through in four games and seal an unexpected 11-8, 7-11, 12-10, 11-9 triumph in 54 minutes.

"I cannot believe it," said Serme.

"Two weeks ago I lost in the first round of the Al Ahram Open and was so far away from this.

"If someone had told me then I’d win the US Open I would have laughed.

"Today was a very difficult test but I just kept pushing and telling myself that I can do it."

In the men’s final, Egypt's world number one Mohamed Elshorbagy secured his second US Open title after England's Nick Matthew was forced to retire in the fifth game following an injury.

It is the third time that Matthew has been forced to retire during major encounters with Elshorbagy inside the past 18 months.

Injury also thwarted the 36-year-old during the 2015 El Gouna International and 2016 Windy City Open.

During the contest triple world champion Matthew started brighter and managed to control the play to open up a 2-0 lead after two punishing games.

However, a hamstring injury he suffered during a lengthy exchange began to take its toll as Elshorbagy levelled the match before Matthew was forced to retire midway through the fifth game.

"This week was about more than squash for me," said Matthew.

"I haven’t won the tournament but I’ve won my squash back - on and off court I’ve found a method to enjoy the game again and play with a smile on my face.

"Ultimately my body just let me down at the end.

"My mind was in the game and I was enjoying it. 

"I love being on this stage and I was a winner this week regardless of tonight."

Elshorbagy led in the fifth when Matthew decided he could not continue, with the score in favour of the Egyptian at 10-12, 12-14, 11-1, 11-4, 3-0.

"I grew up watching Nick playing and he comes from a golden generation," Elshorbagy graciously said of his opponent.

"For me, he's the greatest out of all of them.

"He's the greatest champion I've ever seen in my life, the greatest athlete I've ever seen in my life and the amount I have learned from him is unbelievable."