Norman, who failed to advance from semifinals in the Doha worlds in 2019 with a thigh injury, clocked a winning time of 44.29 seconds.

Three-time Olympic medallist and 2011 world champion Kirani James of Grenada claimed silver with 44.68 seconds, while Briton Matthew Hudson-Smith took bronze (44.66).

World record holder Wayde van Niekerk of South Africa, who set the record of 43.04 seconds when winning gold at the Rio Olympics, finished fifth in 44.97 seconds.

A serious knee injury saw Van Niekerk take a three-year hiatus from the sport and the result is testament to his slow, but committed comeback.

“As the world record holder, this is where I belong,” the South African said.

“This is what I need to fight for. I need to make sure that I do whatever it takes to patiently get myself back to the place where I belong and that is on the podium.

“Fifth this time around, so I am working definitely towards the goal. Hopefully next time, I am on the podium.”

Bahamian star Steven Gardiner, the reigning world and Olympic 400m champion, was a notable absentee from Eugene, missing the worlds because of an inflamed tendon.