The win was Gilbert's second at the warm up race for the Ardennes Classics having also claimed line honours in 2011 as well as finishing runner-up in 2013 and 2008.
"Matthews was the fastest, but I played it well because he had to close the gap to (Bjorn) Leukemans and (Wouter) Poels in the descent and that cost him power," Gilbert said. "I also saw he was closed in in the last corner, but I waited, because I knew from the last times (up the climb), I didn't want to make the same mistake. It was perfect."
Tony Gallopin (Lotto Belisol) rounded out the podium in third place.
With 21km left in the 203km race, Gilbert attacked the peloton to bridge a 15-second gap that a small breakaway had created in a move that lasted 9km which eventually closed down by a chasing peloton.
"I had to choose between waiting or trying and I tried," Gilbert said.
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"Alone against seven riders is not easy with a headwind. And when I came back, the peloton came also back. Eventually it was a performance for nothing; but you never know."
Sport Director Max Sciandri was impressed by his team in controlling the main bunch and then seeing the 31-year-old finish off the job.
"We showed we were the strongest team and, in particular, Philippe showed he was way stronger than a lot of other people," Sciandri said.
"He won a great sprint. He moved the team around pretty well and also made a great move himself. It's quite dangerous to stay out there for seven or eight kilometers after 180km. But he got the job done."
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