The 25-year-old came first in the women’s 10 kilometre free technique mass start race at La Clusaz, France, in a time of 23min 43.5secs and leaped to 654 points in the overall leaderboard, putting her 33 ahead of team-mate Ingvild Flugstad Østberg, who finished third.

Marit Bjoergen completed an all-Norwegian top three, a first for the season.

Sweden’s Stina Nilsson tried all she could to break up the Norway trio, but in the end settled for fourth.

Despite her success, Weng admitted she was surprised when she found out she had won.

“I saw Marit and Ingvild and I thought they passed me,” she said.

“It was great to see my name as the winner.

“I had to give everything I had left.”

In the men’s 15km free technique race held on the same course, defending World Cup champions Martin Johnsrud Sundby was pipped on the line by Norwegian colleague Finn Haagen Krogh by 0.3secs.

The latter waited until the home straight to put in his race-winning move, finishing with a time of 34:09.3.

“I felt in the race I was having a good day,” Krogh said.

“I wanted to stay in the top five and save some energy.

“The last couple of kilometres are always hard and the last two laps were really fast.

“I was fighting with myself to keep up with Martin and he was a little bit unlucky in the corner before the finish because he hit an icy patch.

“I could ski the last curve better and I had more speed to the finish.”

Third place went to Alexander Legkov, who finished a further 3.1secs back.

Sundby remains at the top of the World Cup leaderboard on 340, but Krogh’s victory has cut the advantage to 114 points.

Tomorrow, the men’s 4x7.5km and women’s 4x5km relay will be held on the course.