Titmus won the Australian title on Thursday night in Adelaide in three minutes 59.66 seconds - exactly the same time she clocked at the Pan Pacific Championships last August.

Remarkably, the 18-year-old was competing in Adelaide at the nationals while still in full training and without a taper heading into the meet.

And she had no real competition - Titmus was five seconds in front of the field within 150 metres and eventually won by more than 12 seconds.

"That is pretty crazy to match it," Titmus said of her best time.

"I tried to do the best I can out there by myself, it's a lot tougher.

"Ad much as I tried my hardest tonight, you can always think if you did have someone there, what would happen."

Australian Associated Press