Deignan entered the Roubaix velodrome alone to win the race in 2hrs, 55mins and 3sec, raising her arms in triumph after a courageous 80km solo break.
Dutch rider Marianne Vos was second at 1min 17sec with Italy’s Elisa Longo Borghini third at 1min 47sec.
Trek-Segafredo rider Deignan broke away even before the race reached any of the 30 cobbled sections totalling 29.2km of the rough-hewn stones in Picardy, and rode confidently even when her back wheel span out of control in mud.
With the 132 riders spread out over the course, Dutch star Vos accelerated in pursuit of Deignan with 18km to go, sparking a nasty series of falls among the riders behind her on mud-slick cobbles.
The race itself was originally scheduled for April 2020, then put back to April 2021 only to be postponed a second time due to Covid. (AFP)