The Racing Steps Foundation-backed driver started from sixth position, with the race beginning under the safety car due to the soaking wet conditions on Sunday morning.
When the cars were released after two sighting laps, Barnicoat wasted no time in progressing up the order, with Motopark’s front row starter Sergio Sette Camara spinning down to seventh, and fourth place starter Nick Cassidy going wide. Barnicoat took Chinese racer Guan Yu Zhou into third place by the end of the opening tour.
Barnicoat had work to do though, with the front pair of Maximilian Gunther and George Russell storming off to lead by three seconds.
Barnicoat, who earlier in the weekend, had struggled in qualifying and been unable to make up many places in the previous two races, was handed the lead on lap six when Gunther and Russell collided resulting in race-ending damage for the pair.
Following a further two-lap safety car period, Barnicoat’s lead was untroubled, setting fastest laps to score victory by just under five seconds, from Joel Eriksson with Lance Stroll in third.
“The track was unbelievably slippery in the wet after its recent re-surfacing,” Barnicoat said. “I was initially unsure whether it would be super grippy or slippery.
“I was very happy with my progress on the opening lap to make it into third, and although I benefited, it’s unfortunate for the Hitech GP team that [team-mate] George [Russell] was involved in the collision that handed me the lead.
“From the restart, I just focused on keeping the car on the black stuff. I’m traditionally good in the wet so felt fairly comfortable. The win is great for me and the team, George is more experienced having already had a year of F3 racing, so I expected him to score the team’s first victory.
“Qualifying didn’t go to plan for me earlier in the weekend. It affected my first and second races but I’m so glad that race three has made up for it and I’ve banked good points. I’m ecstatic.”