Frenchman Marchand smashes Phelps's last remaining world record

France's Leon Marchand smashed Michael Phelps's last remaining world record on Sunday, winning the men's 400m individual medley at swimming's world championships in Japan.

Marchand clocked 4min, 02.50 - more than a second faster than Phelps - to finish ahead of American Carson Foster in 4:06.56 and Japan's Daiya Seto in 4:09.41.

Marchand is set to be one of the faces of next year's Paris Olympics and he warned that "the best is yet to come".

"It was insane," the 21-year-old said.

"That was one of the most painful things I did. That was amazing to do it here. The time is crazy."

THIS IS UNBELIEVABLE ??????Leon Marchand beat the longest World Record in the books after 21 years!!!@FFNatation #AQUAFukuoka23 pic.twitter.com/Jkzwmp0xFb

Phelps's record of 4:03.84sec had stood since the 2008 Beijing Olympics and was the longest-held world record in swimming.

Second-place Foster said it was "pretty cool" to watch Marchand break it.

"Obviously the goal is always to win and Leon is a great competitor," said Foster.

"Being the closest person to history was pretty cool, getting a front-row seat to that."

Marchand, who is coached by Phelps's former mentor Bob Bowman, swam the second-fastest 400 IM ever at last year's world championships in Budapest, coming home in 4:04.28.

The Frenchman insisted on Saturday that breaking the record was just "a step in my journey".