The 22-year-old triumphed in Thursday's final to deliver Australia a seventh gold medal of the Tokyo Games.

Making his Olympic debut, the New South Welshman entered the medal race as favourite - he was fastest qualifier and also held the world's quickest time in the event this year.

Stubblety-Cook turned in fourth spot at the halfway stage and was third with 50 metres to swim.

The Australian stormed home to win in two minutes 06.38 seconds from Arno Kamminga (2:07.01) of the Netherlands and Finland's Matti Mattson (2:07.13).

"You can only be an underdog once, right? I had that luxury," he said.

"It was an experienced field but through the heat and semi it was quite exciting that I had a little bit more to give.

"I was happy enough to be here as this time last year we didn't think the Games were going to happen."

Stubblety-Cook admitted being somewhat unnerved by the hot pace set y the Dutchman Kamminga.

"Absolutely. But I was there to execute a race plan," he said.

"And I was obviously pretty happy with the way it pulled off.

"I knew there would be a few people going for it from the start.

"The last time it was won from someone in lane eight, no-one could see him and he held on.

"I was just happy to execute my race plan and do what I do best."

Stubblety-Cook becomes an Olympic gold medallist three years after being a heat swimmer at the 2018 Commonwealth Games.

The self-described perfectionist has been travelling an upward curve ever since, winning his first international medal - 200m breaststroke silver - at the Pan Pacs the following year.

At the 2019 world titles, Stubblety-Cook finished fourth in his pet event and at Australia's selection trials in June for the Tokyo Games, he logged the fastest time of the year, a Commonwealth record 2:06.28.

Australian Associated Press