The 27-year-old rider from Israel-Premier Tech is the first male British victor of the 88-year-old spring classic.
However, a number of riders, including fellow Briton Tom Pidcock, pulled out of the race due to the rainy weather in the Ardennes.
“I’m overjoyed. I’ve watched this race on TV several times and have always wished I had strong legs to try to win it. I’m ecstatic,” Williams exclaimed.
“I saw the ‘300m to go’ line and I thought if I could put five seconds into the group and get near the line, then I could hold on.”
Few anticipated Williams’ unexpected victory, even though she had won the Tour Down Under and had put on a number of impressive performances at the Volta a Catalunya.
He flourished in the soggy circumstances that saw only 44 riders complete and several of the top contenders, including Pidcock, Mattias Skjelmose, and Tiesj Benoot, abandon the race.
