This time places him third in the all-time Australian records, behind Brenton Rickard (58.58 in 2009) and Christian Sprenger (58.79 in 2013), both of whom have won Olympic silver. Williamson, the world champion in the 50m breaststroke in Doha, has secured his spot on his first Olympic team this year. 

His performance in Brisbane positions him as a strong contender challenging Team GB star Adam Peaty's dominance. "I'm lost for words. I told myself this morning if you make it, don't cry on TV," Williamson said.

"All the hard work has been done, I couldn't tell you how many years of hard work. So just step up and do it with a smile. Just do everything with a smile. Sneaking under the minute is a pretty big achievement, so then to sneak under that 59, there's not a lot of guys around the world who have done that, so to be up in that calibre is really impressive and I'm just really happy with the work I've done. 

"It's been a goal of mine (cracking the 59-second barrier). It's something I've been thinking about for a while and have been trying to execute. I'm just happy I've done it and fingers crossed I can come back and swim a little bit quicker tonight."

Ariarne Titmus impressed herself with a strong start at the swimming trials, topping the women's 400m freestyle heats at the Brisbane Aquatic Centre on Monday. The reigning Olympic champion and world record-holder in the event finished with a time of 4:01.57.

"I just feel really excited," Titmus said. "I split 4.01 usually in the heats internationally quite cruisy. But to do it here domestically when I don't really have to go like that, it's quite a surprise when I turn around and see that (time) because I really switched off for the second half of the race. Good confidence for tonight."

Titmus, the defending Olympic champion in the 200m freestyle, outpaced her competitors by over five seconds, with Lani Pallister trailing behind at 4:06.69. Jamie Perkins, a rising 19-year-old, secured third place in the heats with a time of 4:09.95.

In the men's 400m freestyle, 20-year-old Sam Short, the 2023 world champion, clocked 3:48.66, while Elijah Winnington, the 2022 world champion, recorded 3:45.72, setting the stage for another anticipated clash. "I have never been on an Olympic team so there's a bit more nerves in the stomach, but nothing I can't really handle," Short said.

Australia's most decorated Olympian, Emma McKeon, led the times in the women's 100m butterfly heats, clocking 56.75 seconds. Following closely behind were Alex Perkins (57.10) and Brianna Throssell (57.55). 

In the women's 200m individual medley, Ella Ramsey claimed lane four for Monday night's final with a heat time of 2:10.96, ahead of Australian record-holder Kaylee McKeown (2:11.98). McKeown, set to defend her Olympic titles in the 100m and 200m backstroke, has included the medley in her program for the Paris Games starting on 26 July.