The Hitech driver lined up in fourth, but passed Kush Maini for third at Vale on lap four, before swooping past Reece Ushijima for second place at Stowe several laps later.
Championship leader Martins (ART) managed to hold his position for much of the 17-lap race, having taken the lead off the line, but Hadjar eventually made it past two laps from the end around the outside of Stowe.
