Ariarne Titmus hit the wall at Australia's Olympic trials in Brisbane on Wednesday ahead of fellow compatriot O'Callaghan, who also went under her previous world record of 1:52.85, finishing in 1:52.48.

Both Australians, who train under the same coach, Dean Boxall, went at it hard from the get-go, but Titmus, a gold-medal favourite for Paris 2024, managed to hold on until the end despite O'Callaghan pushing her to the limit. The 23-year-old took almost two-thirds of a second off her rival’s previous world mark of 1:52.85 set at last year’s world championships.

"Looking at the results, it's unbelievable. I'm really happy to finally produce a swim in the 200 that I feel like my training reflects," said Titmus. "I think just the field that we have is why we are swimming so fast. We push each other every day. To have five girls under (trainer) Dean (Boxall) in that final is unbelievable. We really don’t see what each other is doing in training, we are very separate: she trains for the sprint events, I train for middle distance. Looking at a world record, I don’t look at who has it. I look at the time. It's a credit to him and the programme.”

Titmus stunned American great Katie Ledecky to clinch gold in the Tokyo Olympics three years ago. She will head to Paris as a red-hot favourite alongside O'Callaghan, who smashed Italian great Federica Pellegrini's 14-year-old world record last year.

The Paris 2024 swimming events are shaping up quite well, as the pair share eight of the 10 fastest times in history, with Ledecky, Canadian phenomenon Summer McIntosh and Hong Kong's Siobhan Haughey all in the chasing pack. So far, McIntosh is the only other swimmer to go under 1:54 this year.

Lani Pallister and Brianna Throssell came third and fourth in Brisbane to position themselves to be part of an ominously fast 4x200m relay team.

Titmus has been in top form in Brisbane, swimming the second-fastest 400m freestyle of all time on Monday as she also prepares to defend that Olympic title. She is also the world record-holder in that event.

After a grandiose season, the 23-year-old is eyeing the Olympic Games ready to pursue the 200-400-800 swimming treble. Her recent triumph in Australia sets the scene for a fierce three-way battle against her fiercest rival Ledecky, O’Callaghan and McIntosh.

“Honestly, the world record is a bonus,” she told The Associated Pess after her splashy win. “I’m happy to finally put together a swim that I know I’m capable of and it’s exciting to do it in my hometown. Now I have the chance to do it again in Paris.”