Thorn, 24, crossed the line 1hr 46min 50sec.

Israel's Sachar Sagiv, who had led the concluding 10 kilometre run for long periods, held on for silver, one second back, with Adrien Briffod of Switzerland taking bronze in 1:46.52.

France's Yanis Seguin missed a podium appearance by a couple of seconds.

Thorn said afterwards he was already looking forward to joining forces in the mixed relay on Saturday as his country seek a clean sweep.

"It means a lot to me now to have won," he said.

"This was my goal, and now I am looking forward to the mixed relay, where we have a really strong team, to see if Norway can win three gold medals here."

Thorn had only arrived in Poland on Monday having travelled back from the World Triathlon Championship Series in Montreal, where the mixed relay race for which he had travelled did not eventually take place.

His bike was further delayed in arriving for several hours.

Speaking about the race today, Thorn added: "It was tough - but it's always tough.

"I was a bit tired after the bike race, but I just hoped for a good run. 

"The first lap was OK, and then I just started feeling better.

"Some of the guys began to put in some surges, and that made it harder, but I knew my sprint was good and I wanted to wait for the finish.

"But then it was so hard and I could see the guys were right behind me, pushing all the way to the line."

Thorn, who won the European junior title in 2018, had taken his turn earlier in the race, leading the 40km bike race for a while in the early stages after The Netherlands' Mitch Kolkman had been the first to emerge from the 1,500m swim in 18min 15sec.

As the race moved into its second phase on a scenic route around the Nowa Huta Lake, only nine seconds separated the top 10.

Thorn remained in touch with the lead as Greece’s Panaglotis Bitados moved to the front and the field made the first of its regular arrivals at the small stadium alongside the lake, where riders completed one lap of the athletics track before moving out and onwards.

Britain's Connor Bentley, world under-23 champion in 2022, was the next to make a move, looking back over his shoulder to see what impact he was making.

But as the field reached the halfway 20km point, the pack had moved back up and Switzerland's Adrien Briffod took up the running in rain that was nothing like as heavy as the downpour the women’s race had endured on the previous day.

As the lead group arrived at the blue carpet of the second transition area, there was a crash farther back in the field which ended with Bob Haller of New Zealand and Zsombor Devay of Hungary having to quit the race and others being delayed.

France's Paul Georgenthum was lead rider when the music stopped after 40km, but it was a marginal distinction, with Germany's Simon Henseleit and Sebastian Wernersen of Norway on his shoulder.

As the field set off on the concluding 10km run which soon involved a jaunt alongside the Lake, the conditions had improved and their shadows were once again sharp on the ground.

Henseleit was soon replaced in the lead as Sagiv, Seguin and Briffod dictated the race pace.

Thorn was never in front, but never far from it, and when the time came his move was decisive.