After soon shelling Andriy Grivko (Astana) and Matteo Fabbro (Katusha-Alpecin) on that climb, Nathan Brown (Team EF Education First-Drapac), De Gendt and teammate Victor Campenaerts built up a maximum advantage of eight minutes.
Eyeing the finish for their fast man, Sonny Colbrelli, Bahrain Merida worked hard to peg some of that time gap back, but De Gendt, alone on the final lap in Yverdon-les-Bains, still held a lead of several minutes.
“I did arrive solo at the finish today," De Gendt said "but this victory is also the merit of Victor. He went out of his way to make sure I had as much advantage as possible.
“We kept on riding full gas and didn’t give up, we just would see where it would take us. And it turned out well.”
“After Victor had done a few last pulls, he got distanced in the local lap. Brown was still making a good impression and I wanted to test him. I immediately got a small gap and I decided to continue on my own, even though it was still a long way to the finish.
“In the past I never had a good feeling here and I wanted to change that. Last week I went on a training camp and that way I prepared for this race. I’ll see tomorrow how I feel for the time trial.
"Today was already a four-hour time trial for me."
Bahrain Merida director Rik Verbrugghe bemoaned the fruitless, solo effort of his team.
"We took responsibility for the pursuit and unfortunately we did not find much collaboration in the other teams."