The 32-year-old defied the extremely wet conditions to clock a time of 40 min 38.2sec and beat nearest challenger Iivo Niskanen of Finland by 37.1 seconds

Compatriot Hans Christer Holund took third place, 49.1 seconds back, to ensure only the third individual World Cup podium of his career. 

Sundby now holds a 384-point advantage over second-placed Sergey Ustiugov of Russia at the top of the overall World Cup rankings.

"Last month has been really good for me training," the Norwegian said.

"It was a difficult race.

"I had amazing skis.

"I had to look for high speed on the snow and constantly change positions.

"I was mentally prepared for an 18km race."

Finland’s Matti Heikkinen, who came fifth today, is 611 points off the pace in the overall World Cup standings in third.

There was also Norwegian success in the women’s 10km interval start classic competition as Marit Bjoergen claimed her 106th World Cup win in dominant fashion.

Bjoergen posted a time of 29:59.0 to triumph by 26.5 seconds over Sweden’s Charlotte Kalla.

Overall World Cup leader Heidi Weng, also of Norway, was 57.2 seconds back in third.

Both Bjoergen and Kalla have competed selectively this season with the former returning from pregnancy and the latter coming back from a health scare during this season’s opening weekend of action in Ruka, Finland in November.

"I had a good training in the last period," Bjoergen said.

"Already at the Norwegian nationals, I knew I was in a good shape.

"Conditions were tricky today but the course was a good test before the World Championships."

Weng’s lead in the overall World Cup standings now stands at 366 points, with fellow Norwegian Ingvild Flugstad Oestberg, a fourth-place finisher today, currently occupying second spot.  

Attention now turns to the FIS Nordic World Ski Championships in Finnish city Lahti, where action is scheduled to begin on Wednesday (February 22).