Matt Walls admitted he was not the most likely candidate to deliver Britain's first track cycling gold of the Tokyo Olympics but that is precisely what he did with a superb win in the men's omnium on Thursday.

On the day Jason Kenny bid farewell to the individual sprint crown he has held since since London 2012, it was his younger room-mate at these Games who delivered victory on the fourth day in the Izu velodrome.

The 23-year-old – whose season was disrupted by a positive test for Covid-19 in March – rode smartly throughout the four-discipline omnium to win with a comfortable final margin of 24 points from Campbell Stewart of New Zealand, with defending champion Elia Viviani taking bronze for Italy.

Walls won the opening scratch race and never trailed again, albeit sharing the lead after the tempo race before moving clear again in the elimination leg.

The Oldham-born rider went into the deciding points race with an advantage of just six points but gained a lap on the field early on, and could then mark his rivals the rest of the way.

Walls won omnium bronze at the world championships in Berlin last year, then took gold against a depleted field at the European championships in November, but was still not regarded as a favourite coming into Tokyo.

"There was a bit of an unknown because the last track race I did was the Euros last year," Walls said.

"But I've been going well on the road, getting in some quality racing this year so I knew I was good coming in. I just didn't know how it would translate on the track, how the tactics would be, because it had been so long.

"But I came into the scratch race feeling good, came away with that win and then I knew I'd got a chance as long as I played it smart. I knew I'd got the legs so it could work out and it did."

Walls tested positive for Covid-19 in late March while racing in Belgium with Bora-Hansgrohe, the WorldTour road team he joined this season.

He was forced to spend two weeks holed up in a Belgian hotel before he could return home, with the experience putting a significant dent in his season as he did not race on the road again until the Tour de Suisse in June.

Britain had been made to settle for silver in the women's team pursuit and men's team sprint earlier in the week, while another event they had previously dominated – the men's team pursuit – ended in a disappointing seventh place.

But Walls, held out of that pursuit in order to focus on the omnium, has changed the narrative for a team seeing their reign of dominance come to an end.

"It never looked in doubt from the moment he rolled off the start line," Kenny said of Walls after settling for eighth in the sprint himself. "He's my room-mate but I can't take all the credit, obviously.

"He's just a proper racer. He lives to race and lets his racing do the talking. He's a proper hard-working young lad, as good as anyone. You get the feeling watching him that he's not thinking about it, it's happening naturally and that's the best way to be."

This was a first men's Olympic omnium gold for Britain, with Ed Clancy having taken bronze in London in 2012 and Mark Cavendish silver in Rio.

Walls will now look to double up in the Madison this weekend, riding alongside his Manchester house-mate Ethan Hayter – the pair also live with Bahrain-Victorious rider Fred Wright – having been up against Hayter in selection for the omnium.

"He was pretty good about it actually," Walls said of the selection battle. "And we ride the Madison together on Saturday, which will be fun. We're both going pretty well so it will be interesting to see what we can do there."