That opened the door for the mainland Chinese duo, and they grabbed their chance in the final late on Tuesday.

Yang finished first in a time of one minute and 54.92 seconds – exactly a second slower than Haughey’s best time in an Olympic-standard 50m pool. Silver went to Mollie O’Callaghan of Australia, in 1:55.22, and Tang was third in 1:56.25.

Chillingworth finished in 2:11.88, faster than his city record of 2:12.17, set in April. But as he touched at the finish, his leg movement was deemed to be a butterfly kick.

“It was quite clear on the video replay, and we will not appeal the decision,” head coach Chen Jianhong said. “We are quite happy with his performance, had it not been for the final touch. We hope he can learn from the mistake.

“Our target for him remains the 2024 Paris Olympics. We consider Adam a potential qualifier for Hong Kong.”

Late on Tuesday, a capacity crowd was deprived of one star as Caeleb Dressel withdrew, but saw the one they wanted, roaring local hero Kristof Milak to a world record.

Milak won the event he dominates, the 200m butterfly, while Dressel, the defending champion, pulled out of the 100m freestyle semi-finals and mixed medley relay just before the session.

That called into question the much-anticipated showdown between the two in the 100m butterfly, where Dressel holds the world record and edged Milak in the Olympic final last year. The heats are on Thursday morning.

“Whether Dressel is there or not, I will stand there and do everything I can in the 100 fly for a gold or a silver or a world record, this is all my focus,” Milak said after winning the 200m butterfly.

“Of course it would be better if my big opponent was here, at home as it were, for a head-to-head fight.”

Dressel had swum in the heats in the 100 free, finishing second-fastest to Romanian teenage sensation David Popovici. Dressel won the event at the last two world championships and at last year’s Olympics.

Milak won his final in 1:50.34 to shave 0.39 seconds off the world record he set winning his previous world title in 2019. It was Hungary’s first gold of the competition.

“It’s a completely different experience to go out there to the pool in front of so many people who are rooting for you and who you are swimming for, it’s a mutual thing,” Milak told Hungarian television.

“When I stepped on the blocks and got ready, I felt as if I was in a dream, a feeling of being so in the flow. This is my home, my pool. I train here, I race four, lane four belongs to me. I really wanted to show something big for these fantastic people.”

Without Dressel, who had swum the butterfly leg when they finished fifth in Tokyo, the United States took gold in the 4x100m mixed medley relay ahead of Australia and the Netherlands.

Olympic champion Bobby Finke made another late surge to grab gold in the men’s 800m freestyle.

Chillingworth ready to go solo after Hong Kong’s winning feeling in relay

Ukrainian Mykhailo Romanchuk led for half the race and went into the final turn first with Finke back in fourth. As he did in Tokyo, the American’s last lap sprint carried him to victory. His time of 7:39.36 was an American record.

German Olympic open-water champion Florian Wellbrock also slipped past his training partner Romanchuk at the end to grab silver. Wellbrock invited Romanchuk to join him in Magdeburg following the Russian invasion of Ukraine in February.

Another American, Nic Fink, won the men’s breaststroke 50m sprint. He edged 100m gold medallist Nicolo Martinenghi by a microscopic 0.03 sec.