Titmus pips Ledecky to world title, Peaty sets record and Sun sees off Horton

American 22-year-old Ledecky had won three world titles in the event, and is the reigning Olympic champion, but on this occasion 18-year-old Titmus surged past her on the final length to take gold.

Titmus touched in three minutes, 58.76 seconds and played down her success, calling Ledecky "the greatest ever" and predicting "a real battle" between the pair at the Tokyo Olympics next year.

That could prove one of the highlights of the 2020 Games pool programme, with Ledecky needing to put together a more complete swim than she produced in Gwangju.

Ariarne Titmus from @SwimmingAUS swam for GOLD in the Women's 400m Freestyle! Well done! #FINAGwangju2019 pic.twitter.com/C0cbe4ubK5

— FINA (@fina1908) July 21, 2019

Ledecky claimed her legs felt "just dead" in the closing metres, saying on the Olympic Channel: "Obviously Ariarne took advantage of that and had a heck of a swim.

"Obviously this stings a little, it's unfamiliar and different, and I need to rebound from this and get my fight back."

American Ledecky has 14 world golds in all, and until Sunday's jarring setback had only failed to triumph at the championships in one previous final when she took 200m silver in Budapest two years ago.

Great Britain's Adam Peaty broke his own world record in the 100m breaststroke semi-finals, becoming the first man to push through the 57-second barrier as he clocked 56.88secs.

"Obviously I've been chasing that for years now," said Peaty.

#SWIMMING - Men's 100m Breaststroke Semifinal@adam_peaty set a NEW World Record!!! 56.88 #FINAGwangju2019 pic.twitter.com/ZpAoKBAKp0

— FINA (@fina1908) July 21, 2019

Australian Mack Horton refused to join champion Sun Yang on the medal podium following the men's 400m freestyle.

Horton took silver in 3:43.17 as China's Sun touched first with 3:42.44 to land gold in the event for the fourth successive games.

Sun served a short doping ban in 2014. He is currently the subject of an appeal by the World Anti-Doping Agency [WADA] to the Court of Arbitration for Sport, with WADA questioning a decision by swimming's global governing body FINA not to punish Sun over allegations stemming from a visit by out-of-competition testers in September 2018.

Sun denies all wrongdoing and has requested a public hearing.

Horton said of losing to Sun: "I think you know what the rivalry is like. I don't think I need to say anything, I think his actions and how it's been handled speaks louder than anything I'll ever say."

#SWIMMING - MEN'S 400m FREESTYLE SUN Yang made 4 in a row!The Chinese is the first in the history of the #FINAWorlds to win the 400m Free for 4 consecutive times!#FINAGwangju2019 pic.twitter.com/I78ulh9L7h

— FINA (@fina1908) July 21, 2019

The United States won the men’s 4x100m freestyle relay in a championship record of 3:09.06, with Russia taking silver and Australia bronze.