Au had previously claimed just three games against the eight-time world champion across their previous 17 World Tour meetings.

The Hong Kong player made a stunning start to their latest clash at Philadelphia's Drexel University, winning the opening two games 11-5, 11-5.

She could have been forgiven for thinking her chance to beat David had slipped away when the Malaysian hit back to level the contest.

Au would hold her nerve in the decisive fifth game to seal a 11-5, 11-5, 10-12, 8-11, 11-7 victory.

"I feel really, really happy right now," said Au.

"To beat Nicol - in my first ever win on the glass court at this event - is a massive result and makes all the hard work over the summer feel worth it.

"I had to come out in the fifth and imagine it was the start of the match again.

"I forgot about the score and just tried to play each point.

"I had already booked my travel for tomorrow so I will have to change my flights."

Au will now face England's Laura Massaro, after she beat her compatriot Emily Whitlock in straight games.

Massoro eased to a 13-11, 11-6, 11-6 victory, winning after 32 minutes of play.

Nour El Sherbini beat England's Victoria Lust 11-2, 11-2, 11-0, with the world number one now set to face her fellow Egyptian Nour El Tayeb, who overcame her compatriot Salma Hana Ibrahim 8-11, 14-12, 13-11, 11-6.

Defending men's champion Mohamed Elshorbagy came through a tricky tie against his fellow Egyptian Mohamed Abouelghar 11-8, 7-11, 11-2, 11-6.

His reward will be a quarter-final match against Simon Rösner, with the German beating Mexico’s Cesar Salazar 11-8, 11-8, 11-13, 11-1.

England are assured of a men's semi-finalist, with Nick Matter set to meet Daryl Selby in the last eight.

Matthew, a two-time winner of the event, eased past France's Gregoire Marche 11-8, 11-6, 11-6.

His compatriot Selby had a far tougher test, ultimately beating Egypt’s Tarek Momen 11-9, 8-11, 12-10, 7-11, 11-8.