Championship leader Daniel Guinchard led home Hillspeed teammate Leandro Juncos to clinch his second win of the season in race two at Oulton Park.
Guinchard survived a safety car restart and intermittent weather to win from pole, with Juncos joined on the podium by KMR Sport's race one winner Alex O'Grady.
There was plenty of drama again pre-race, as rain fell again during the build-up, but this time around it stopped before the cars were released. All the field eventually opted for slicks, but only after several teams had already carried out a few tyre changes.
Drama continued on the formation lap, when Josh McLean hit the barriers, leading to an aborted start and a reduced race distance of 16 minutes, and cars held on the grid.
When the race eventually got underway, Guinchard made a good start to hold the lead down to turn one, while Juncos made big progress from fifth to move into second within a few corners, with the Elite Motorsport trio of Alex Kattoulas, Ary Bansal and Isaac Phelps demoted by the Argentinean.
Green flag running lasted until lap two however, as Mayer Deonarine found the barriers at Shell Oils, with spots of rain falling at the far end of the circuit.
The race resumed with five minutes remaining, and Guinchard immediately reestablished a lead of around a second, while Kattoulas pressured Juncos. Behind, O'Grady was making moves again and gained two spots on the restart lap to move into fourth.
The Irishman then slotted up the inside of Kattoulas at Old Hall on the penultimate lap to secure the final podium spot. His charge continued, but just ran out of time to progress further, and he finished the contest just three tenths behind Juncos, as Guinchard stormed to victory by three seconds.
Behind the top-three entertainment, Kattoulas settled for fourth ahead of Phelps while Douglas Motorsport's Luke Hilton moved up to sixth from ninth on the grid.
Stefan Bostandjiev was another to make excellent progress as he claimed seventh from 12th, finishing just ahead of Arden's Leon Wilson.
After a handful of incidents, Bansal fell from third to ninth, finishing just 0.065s ahead of Graham Brunton Racing's Callum Baxter, who completed the top-10.
The final race of the weekend, the top-12 reverse grid contest, is due to commence at 17.05.
GB4 Championship, partnered by the BRDC, Oulton Park provisional race two result:
1. Daniel Guinchard, Hillspeed, 8 laps
2. Leandro Juncos, Hillspeed, +3.067s
3. Alex O'Grady, KMR Sport, +3.401s
4. Alex Kattoulas, Elite Motorsport, +3.877s
5. Isaac Phelps, Elite Motorsport, +4.005s
6. Luke Hilton, Douglas Motorsport, +5.404s
7. Stefan Bostandjiev, Pace Performance, +6.131s
8. Leon Wilson, Arden Motorsport, +6.791s
9. Ary Bansal, Elite Motorsport, +6.962s
10. Callum Baxter, Graham Brunton Racing, +7.027s
11. Alex Berg, Graham Brunton Racing, +7.341s
12. Dayton Coulthard, Douglas Motorsport, +7.473s
13. Jason Pribyl, ADM, +7.505s
14. Luca Magnussen, Fortec Motorsports, +7.797s
15. Thomas Ingram Hill, Fortec Motorsports, +9.324s
16. Enzo Hallman, Douglas Motorsport, +9.751s
17. Holly Miall, Fox Motorsport, +13.406s
18. Lily-May Watkins, KMR Sport, +14.532s
19. Caitlyn McDaniel, Fox Motorsport, +40.401s
DNF. Ava Dobson, Arden Motorsport, 7 laps
DNF. Megan Bruce, KMR Sport, 7 laps
DNF. Jack Taylor, Fortec Motorsports, 4 laps
DNF. Mayer Deonarine, Graham Brunton Racing, 1 lap
DNF. Josh McLean, Pace Performance, 0 laps
