The Australian sprint star came in a run along the barriers late to overtake Sam Bennett (Deceuninck-QuickStep) on a very wet stage finish in Templeuve.
"The whole day was quite nice until it started raining with one hour to go," Ewan said after the stage. "The rain and cobbles on the finishing circuit made it a super nervous run-up to the final sprint.
"My team did a good job in keeping me close to the front. In the end, I was a little bit far, but that was perfect since my competitors launched the sprint very early and I could come back in the final metres."
Ewan will go into Stage 2 as the leader of the tour, with a class field of sprinters including Bennett, Arnaud Demare (Groupama-FDJ), Bryan Coquard (B&B Hotels-Vital Concept), Mark Cavendish (Bahrain-Merida), Tim Merlier (Alpecin-Fenix) and Nacer Bouhanni (Arkea-Samsic) all out to take their own sprint wins.
"I want to defend the leader's jersey tomorrow and maybe even the day after tomorrow if I have good climbing legs," said Ewan. "But the fourth stage will be too hard for me. With Philippe Gilbert we have someone in great form and he knows the local roads. So he will target the GC for team Lotto Soudal."