Xcel Motorsport's Rowan Campbell-Pilling topped the Thursday test at the Circuit de Barcelona-Catalunya, as preparations began for the season finale at the Spanish F1 venue.
The 25 drivers entered for this weekend had a total of four hours track time in the session, and it was the British driver who emerged on top of the late flurry of laps, setting a 1m32.990s to put himself just 0.086s ahead of Rodin's Martin Molnar, who also led the times in the final 15 minutes.
The best times came after a brief sprinkling of rain in the final hour, with Hitech's Deagen Fairclough just over a quarter of a second away from P1 with the third best time.
The returning JHR Developments team looked like they'd never been away by going fourth fastest with series newcomer Lewis Wherrell, who was just five thousandths of a second clear of fellow newcomer Ary Bansal. The Indian driver, racing with series newcomers TJ Speed led a significant portion of the four hour test, before being shuffled down to fifth in the final stages.
Rodin's Maxim Rehm was sixth quickest and 0.027s further back, and 0.022s clear of Kyuho Lee, who was the lead Elite Motorsport runner in seventh.
Patricio Gonzalez was the lead VRD Racing runner, two hundredths of a second clear of championship leader Nikita Bedrin, who is sporting a new livery ahead of his likely title-clinching event.
Xcel's local driver Lucas Fluxa completed the top-10, which was covered by 0.582s.
With debutants Wherrell and Bansal inside the top-10, there were strong performances from the other crop of newcomers with Bansal's teammate Arjen Kraling 12th, GB4 runner-up Fred Green 14th for Elite Motorsport and Hitech's F4 runner-up Theo Palmer 18th, and within a second of the outright pace.
Thomas Ingram Hill (JHR) completed the top-20, while fellow GB4 graduate Matan Achituv completed the 25 runners, with the field covered by 2.2 seconds.
The season finale weekend continues with three free practice sessions at 11.00, 14.20 and 16.20 local time.
GB3 Championship, partnered by the BRDC, Circuit de Barcelona-Catalunya, Thursday test result:
1. Rowan Campbell-Pilling, Xcel Motorsport, 1m32.990s
2. Martin Molnar, Rodin Motorsport, +0.086s
3. Deagen Fairclough, Hitech, +0.251s
4. Lewis Wherrell, JHR Developments, +0.379s
5. Ary Bansal, TJ Speed Motorsports, +0.384s
6. Maxim Rehm, Rodin Motorsport, +0.411s
7. Kyuho Lee, Elite Motorsport, +0.433s
8. Patricio Gonzalez, VRD Racing, +0.470s
9. Nikita Bedrin, VRD Racing, +0.490s
10. Lucas Fluxa, Xcel Motorsport, +0.582s
11. Abbi Pulling, Rodin Motorsport, +0.598s
12. Arjen Kraling, TJ Speed Motorsports, +0.619s
13. Aurelia Nobels, Hillspeed, +0.762s
14. Fred Green, Elite Motorsport, +0.779s
15. Peter Bouzinelos, Hillspeed, +0.791s
16. Dante Vinci, Hillspeed, +0.848s
17. Yuhao Fu, Hitech, +0.946s
18. Theo Palmer, Hitech, +0.972s
19. Ricardo Baptista, Xcel Motorsport, +1.229s
20. Thomas Ingram Hill, JHR Developments, +1.265s
21. Flynn Jackes, Elite Motorsport, +1.311s
22. Rodrigo Gonzalez, VRD Racing, +1.338s
23. Leon Wilson, Arden Motorsport, +1.911s
24. Jason Pribyl, Nitrous Competitions ADM Racing, +1.916s
25. Matan Achituv, Arden Motorsport, +2.201s