ART Grand Prix driver Marvin Kirchhofer narrowly held off his former German F3 teammate Emil Bernstorff to win the feature race at Silverstone.
Rapid off the line, Kirchhofer managed to keep his Bernstorff at bay into Turn 1, albeit the Arden driver seriously threatened for the lead for the remainder of the opening lap.
However, Kirchhofer weathered the early storm and soon established a gap of a second and a few tenths, which he maintained over the first half of the race.
Behind the leading duo, third-placed Alex Palou allowed fellow rookie Matt Parry through at the start and was passed by the Brit's Koiranen teammate Jimmy Eriksson next time around.
Palou ran a solid fifth for the next few laps, but the newcomer's car soon developed an issue, first allowing championship frontrunners Luca Ghiotto and Esteban Ocon through and then losing all speed.
Out front, Bernstorff and Parry had both kept in touch with the leader at halfway point, the former soon returning to within a second of Kirchhofer. With three laps to go, the gap between the leading duo was at just half a second.
On the penultimate lap, Kirchhofer slowed in the first sector and allowed Bernstorff to get alongside him. The pair ran side by side by for a few corners, before Kirchhofer claimed the inside line into Copse, maintaining the lead.
His Arden rival never got this close again over the remaining lap and a half, allowing Kirchhofer to secure the win.
While Parry brought the car home to claim a maiden GP3 podium, his teammate and 2014 Silverstone winner Eriksson was all by his lonesome for much of the race in fourth, unable to keep up with the top three but keeping clear of fifth-placed Ghiotto.
However, the Swede started to lose time in the final minutes and was reeled in by the championship leader, who eventually passed him round the outside on the final lap.
Ocon took sixth, ahead of Kevin Ceccon and Ralph Boschung, who is set to start the reverse-grid race from pole for a second successive weekend.
Artur Janosz and Matheo Tuscher scored their first points of the season in ninth and tenth respectively.
|1||M.Kirchhofer||ART Grand Prix||37'02.785|
|2||Emil Bernstorff||Arden International||0.302|
|3||Matt Parry||Koiranen GP||2.421|
|5||Jimmy Eriksson||Koiranen GP||10.511|
|6||Esteban Ocon||ART Grand Prix||11.459|
|7||Kevin Ceccon||Arden International||12.274|
|8||Ralph Boschung||Jenzer Motorsport||18.732|
|10||Matheo Tuscher||Jenzer Motorsport||21.197|
|12||Adderly Fong||Koiranen GP||30.193|
|13||Alfonso Celis||ART Grand Prix||33.591|
|14||Alex Bosak||Arden International||38.177|
|15||Seb Morris||Status Grand Prix||38.266|
|16||Pal Varhaug||Jenzer Motorsport||38.456|
|19||Alex Fontana||Status Grand Prix||40.052|
|21||Zaid Ashkanani||Campos Racing||55.378|
|22||Sandy Stuvik||Status Grand Prix||1'04.044|
|-||Alex Palou||Campos Racing|