Il Nuovo Postiglione - Ledecky lays down an early marker at world swimming championships

In the women's 400m freestyle qualifying, the 25-year-old American was the only swimmer to break four minutes, finishing in 3min 59.79sec, 3.40sec ahead of Canadian 15-year-old sensation Summer McIntosh.

Ledecky's greatest rival, Australian Ariarne Titmus, is skipping the championships. Titmus overhauled Ledecky on the final lap in the last worlds in 2019. The first time Ledecky had lost in the event in a major championship.

Titmus then edged Ledecky in the Olympic final last year and ended the American's eight-year grip on the world record in May, with a time of 3min 56.40sec.

On Saturday, Ledecky may have left the field trailing in her wake but she was still more than 2 seconds behind her phantom foe.

Home favourite Katinka Hosszu opened the championships, in the women's 200m individual medley first round.

Hungary's 'Iron Lady', who won two world titles the last time the championships were in Budapest, qualified 11th 2.36 slower than American Alex Walsh and five-and-a-half seconds outside her own world record.

At 33, the question remains whether she can shake off the rust.

Other big names also swum unspectacular times while still ensuring they qualified.

Australian phenom Kaylee McKeown was only seventh while champion Yui Ohashi from Japan qualified 12th.

- 'Chance to roar' -

Lukas Martens, the 20-year-old German who this season sliced three seconds off his best time while swimming 3:41.60, the fastest 400m free since 2017, was more than three-and-a-half seconds off that time as he qualified fourth fastest in the event.

Austrian Felix Auboeck scorched through the last 100m in the final heat to lead all qualifiers in 3min 43.83.

Surprise Olympic champion, Tunisian Ahmed Hafnaoui did not race.

American teenager Torri Huske led the qualifiers in the women's 100m butterfly, followed by France's Marie Wattel and Zhang Yufei who is chasing China's eighth championship medal in the event.

Dylan Carter from Trinidad, twice a short-course world championship medallist, beat 23 seconds for the first time in his career to lead the 50m butterfly qualifying in 22.87.

American Caeleb Dressel then won the seventh heat and mustachioed Italian Thomas Ceccon the last, both in 22.88.

World record holder Andrii Govorov from Ukraine was seventh and Nicholas Santos was 13th, but only two-thirds of a second separated the qualifiers in an event decided by fingernails.

With Adam Peaty, the Briton who has dominated the men's 100m breaststroke, absent, perennial runner up, Dutchman Arno Kamminga started his chase for a first gold when he was fastest in qualifying ahead of Nic Fink of the USA.

Two 20-year-olds, Frenchman Leon Marchand and American Carson Foster, were fastest in the men's 400 medley but the old guard were close behind. world champion Chase Kalisz was third fastest followed by Japanese reigning world champion Daiya Seto.

Home fans had a final chance to roar in the last event of the morning after Hungary chased the USA home to qualify third in the men's 4 x 100m freestyle relay.

S.Maiolo--INP