The only way is down for Ariarne Titmus. Another race for the Brisbane teenager, this time in the company of the wondrous Katie Ledecky, produced another milestone and set the scene for an intriguing 400m showdown later in the Pan Pacs meet in Tokyo.

Titmus, still just 17, ticked off her first goal by claiming Jess Ashwood's Australian 800m record, touching the wall at the Tatsumi International Swimming Centre in 8min 17.07s. It was almost three seconds faster than her gold medal swim at the Commonwealth Games.

That time was good enough for second, well behind the peerless Ledecky but ahead of her American team-mate Leah Smith, who pushed Titmus all the way through a thrilling final 100m of the race.

Her arms were burning late but Titmus absorbed every jab Smith threw in the end stages of the race, kicking strongly to battle her way to the wall in a swim that will only give her further confidence in the event heading towards the Tokyo 2020 Olympics.

The 400m remains the focus for Titmus, although she had increased her endurance training under coach Dean Boxall to see how low she could go in this event. The gap to Ledecky was significant – she rattled off an 8:09.13 in a new championship record – but Titmus is at the stage of her career where she can shed chunks of time in a hurry.