Kevin Mills Racing ended the Donington Park GB4 media day test on top of the times, courtesy of 2022 race-winner Tom Mills.
The youngster, who has yet to confirm his plans for the 2023 season, was shaking down his team's newly-acquired third car, and put his experience to good use by topping the times in each of the four sessions today.
It was the second of the day's four sessions that proved the quickest, with all 11 runners that opted to use timing transponders setting their best times during the final 30 minutes of the morning.
Mills ended the day 0.339s clear of Elite Motorsport's Josh Irfan, who was sampling GB4 machinery at the East Midlands circuit.
Irfan was 0.083s ahead of Fox Motorsport's Liam McNeilly, who has been a regular contender towards the top of the timesheets throughout pre-season testing, and was the fastest confirmed entrant for the 2023 season today.
Colin Queen was fourth quickest for Fortec, though he missed the final session after an accident in the session three, but was still only just half a second away from top spot.
S5000 convert enjoyed his and the Evans GP team's first taste of GB4 machinery and was fifth quickest, within a second of the outright pace, with Harri Reynolds, another driver eyeing a GB4 move, setting the sixth quickest time for Elite.
The second Fox Motorsport machine of Sid Smith was seventh, 0.014s ahead of Kevin Mills Racing's Jack Clifford, with his teammate Jeremy Fairbairn ninth.
Harry Burgoyne, the youngest driver in the field, completed the top-10 for Graham Brunton Racing, with Oldfield Motorsport's Jason Conzo ending his first day in GB4 machinery with the 11th quickest time.
In total, 13 GB4 cars ran today, with privateer Dylan Hotchin enjoying his first full test day in GB4, while Fortec Motorsport ran Dan Hickey. Both completed testing without transponders.
The quickest driver to have confirmed their place on the grid, McNeilly, said: "We managed to get some good laps in this morning, and to be the fastest confirmed driver is always nice. Obviously you want to be fastest but I'm happy with how today has gone.
"We're adapting well, there's been some good running today and it was my first day on the GP circuit in a GB4 so we've made a strong start in pre-season.
"We still have some time to find in the wet but I think our dry pace is strong and it showed, as we were only a few tenths off someone who has raced in this series for a year. It's quite good for us."
GB4 Championship, partnered by the BRDC, Donington Park media
day test result:
1. Tom Mills, Kevin Mills Racing, 1m28.172s
2. Josh Irfan, Elite Motorsport, +0.339s
3. Liam McNeilly, Fox Motorsport, +0.422s
4. Colin Queen, Fortec Motorsport, +0.553s
5. Cooper Webster, Evans GP, +0.919s
6. Harri Reynolds, Elite Motorsport, +1.126s
7. Sid Smith, Fox Motorsport, +1.362s
8. Jack Clifford, Kevin Mills Racing, +1.376s
9. Jeremy Fairbairn, Kevin Mills Racing, +2.165s
10. Harry Burgoyne, Graham Brunton Racing, +2.300s
11. Jason Conzo, Oldfield Motorsport, +3.938s