Sawt Falasteen - McKeown narrowly misses world record as Chalmers lights up 100m free

Olympic 200m and 400m freestyle champion Ariarne Titmus was also on fire in Melbourne, rebounding from her shock loss to Mollie O'Callaghan in the 200 to clock the second-best 800 of the year.

McKeown lowered American rival Regan Smith's world best in March with a sizzling 2:03.14 and hit the wall in an eye-popping 2:03.70 -- the fourth-quickest time in history.

Jenna Forrester came second, a whooping seven seconds behind.

"Really happy with that, it's the second-fastest time I've ever posted so do that here, it's good race practice," said the 21-year-old Olympic and world champion. "My legs died in the final 15 but I'm a happy girl."

McKeown was under world record pace at the halfway mark and will head into the championships in Japan next month as the hot favourite.

Her exploits followed her third-fastest 100m backstroke in history on Wednesday, touching in 57.50, just 0.05 seconds shy of her own world mark.

Chalmers was never threatened as he surged to the wall in 47.44, the second-best this year behind China's Pan Zhanle and quicker than reigning Romanian world record holder David Popovici.

Teenager Flynn Southam (47.77) also qualified.

"I'm excited, I had a lot of energy with all the young boys alongside me," said Chalmers, who came second to American arch-rival Caeleb Dressel at the Tokyo Olympics after winning gold in Rio in 2016.

"I'm loving it and so happy doing this. I can't wait to get on the world stage in a couple of weeks."

Titmus led from start to finish to touch in 8:15.88 and take out the 800m title, with only American great Katie Ledecky, who beat her to gold at the Tokyo Olympics, better this year.

"It's two seconds off my best, so not too bad," said Titmus.

Lani Pallister (8:20.56) came second and will join her in Japan.

Elsewhere, Commonwealth champion Elizabeth Dekkers scorched through the 200m butterfly in a personal best 2:05.26, behind only Canadian sensation Summer McIntosh this year. Abbey Conner (2:07.61) also qualified.

Thomas Neill won the men's 200m medley in a personal best 1:57.74, matching the automatic qualifying time, but Tokyo Olympic bronze medallist Brendon Smith missed out.

Abbey Harkin (31.14) took out the women's 50m breaststroke while Isaac Cooper (24.56) won the men's 50m backstroke.

J.AbuHassan--SF-PST