The Enduro Motorsport McLaren 720S GT3 of Morgan Tillbrook and Marcus Clutton set the fastest time in FP1 at a cloudy Donington Park on Saturday morning.
The #77 car hit the front early and never relinquished it, in a session truncated by a five-minute red flag period.
Gus Burton/Will Burns were on top in GT4, as Century Motorsport look to build on their positive start to the season.
GT3
The two Barwell Motorsport Lamborghini Huracan GT3 Evos of Dennis Lind and Sandy Mitchell were first out of the pitlane, and it was Championship leader Lind who went top of the timesheets first with a 1:28.909 ahead of Beechdean AMR‘s Jonny Adam.
Adam was soon usurped for second by Mitchell, the reigning British GT champion going half a tenth behind his Barwell team-mate within the opening ten minutes of the hour-long session.
Marcus Clutton shot up to sixth in the Enduro Motorsport McLaren, with a 1:30.552, before several of the ten GT3 runners had set a representative lap.
Lind returned to the pits early on, while the RAM Racing Mercedes-AMG GT3 Evo of Ian Loggie took its time in heading out on track.
Michael Igoe overtook Martin Plowman to go sixth in the WPI Motorsport Huracan, a car which endured a torrid time in the Silverstone 500 last time out.
It’s believed a run-out in GT Cup between meetings has helped the team identify the issue with the car which won the first race of the season, so we shouldn’t see the #18 Lamborghini as low as 16th in qualifying this weekend.
Lewis Proctor (Balfe Motorsport) went quicker than Richard Neary (Abba Racing) to go eighth, while positions elsewhere started to stabilise.
Clutton went quickest with a 1:27.550, half a second ahead of Scott Malvern in the Team Parker Racing Porsche 911 GT3. Malvern and Nick Jones won here in the Bentley Continental GT3 last August, and will hope a winter change of machinery doesn’t hinder their prospects in Leicestershire this weekend.
Yelmer Buurman and Michael Igoe swapped places as they duelled for sixth, with the Mercedes finding half a tenth on the WPI man.
Championship leader Lind went ahead of Scott Malvern at the half-hour mark, less than half a second off the Enduro McLaren which still topped the times.
Phil Keen overtook his old Barwell team-mate Adam Balon with a 1:28.237, going just half a tenth clear of the #1 Lamborghini. He then boxed to hand back over to Igoe, who also won here last year alongside Lamborghini Squadra Corse man Andrea Caldarelli.
The red flag flew with 23 minutes remaining, with the session restarting with 18 on the clock.
There were just over 15 minutes left by the time the drivers crossed the line to set their first timed laps after the red flag, but no-one improved their times in GT3 and Clutton/Tillbrook topped the session ahead of Loggie/Buurman and Machitski/Lind.
Jones/Malvern were fourth, ahead of Keen/Igoe and Mitchell/Balon. Jonny Adam/Andrew Howard were eighth ahead of Fletcher/Plowman, with Stewart/Lewis Proctor rounding out the GT3 times.
GT4
The Jenson Team Rocket RJN McLaren 570S GT4 of James Kell was a little later out of the pits than its competitors, as was Sennan Fielding in the Steller Motorsport Audi R8 GT4.
Fielding set the fastest GT4 time early on, but it was quickly beaten by Gus Burton and Jake Giddings in the Century Motorsport BMW M4 GT4 and the Ciceley Motorsport by Car Gods Mercedes-AMG GT4 respectively.
There weren’t too many changes for position after the first representative laps were set for the opening 15 minutes, until Scott McKenna took the TOYOTA GAZOO Racing UK GR Supra GT4 to the top, quickly beaten by Championship leader Burton by four tenths.
Darren Burke improved in the Newbridge Motorsport Aston Martin Vantage GT4 to go ahead of Chris Salkeld (Century) and Jamie Stanley (Fox Motorsport McLaren), to go fourth in class after 20 minutes.
He then moved past Richard Williams in the Steller Audi, Burke replacing Darren Turner in the car which took GT4 top honours at Silverstone last time out.
James Kell and Will Burns received track limits warnings at McLeans and the Old Hairpin respectively, as the session passed half-distance.
Charlie Robertson shot up to 18th after the red flag in the Assetto Motorsport Ginetta G56, as Nick Halstead slipped to the bottom of the timesheet in the Fox McLaren.
His next lap was even better and moved him up to 14th, while Matt Cowley also improved in the Academy Motorsport Ford Mustang.
Gus Burton/Will Burns finished the session on top in GT4, ahead of Ferguson/McKenna and Whitmore/Giddings rounding out the top three.
Robertson/Sansom came in fourth, ahead of Topham/Burke and Williams/Fielding.
A throng of McLarens followed, with Valente/Benyahia and Marshall/Brown ahead of Will Moore/Matt Cowley in the Mustang.
Chris Salkeld and Andrew Gordon-Colebrooke led home Milner/Hayek, Kell/Collard and Halstead/Stanley.
2021 Donington Park Free Practice 1 Results:
| Pos. | No. | Name | Team | Car | Time/Gap |
| 1 | 77 | Tillbrook/Clutton | Enduro Motorsport | McLaren 720S GT3 | 1:27.550 |
| 2 | 6 | Loggie/Buurman | RAM Racing | Mercedes-AMG GT3 Evo | +0.238 |
| 3 | 63 | Machitski/Lind | Barwell Motorsport | Lamborghini Huracan GT3 Evo | +0.454 |
| 4 | 66 | Jones/Malvern | Team Parker Racing | Porsche 911 GT3 RSR | +0.483 |
| 5 | 18 | Keen/Igoe | WPI Motorsport | Lamborghini Huracan GT3 Evo | +0.532 |
| 6 | 8 | R Neary/S Neary | Team Abba Racing | Mercedes-AMG GT3 | +0.662 |
| 7 | 8 | Mitchell/Balon | Barwell Motorsport | Lamborghini Huracan GT3 Evo | +0.741 |
| 8 | 7 | Howard/Adam | Beechdean AMR | Aston Martin Vantage GT3 | +0.945 |
| 9 | 11 | Fletcher/Plowman | Paddock Motorsport | Bentley Continental GT3 | +1.511 |
| 10 | 5 | L Proctor/S Proctor | Balfe Motorsport | McLaren 720S GT3 | +1.748 |
| 11 | 57 | Burton/Burns | Century Motorsport | BMW M4 GT4 Evo | +8.201 |
| 12 | 15 | Ferguson/McKenna | TOYOTA GAZOO Racing UK | Toyota GR Supra GT4 | +8.346 |
| 13 | 25 | Whitmore/Giddings | Ciceley Motorsport by Car Gods | Mercedes-AMG GT4 | +8.811 |
| 14 | 56 | Robertson/Sansom | Assetto Motorsport | Ginetta G56 GT4 | +8.945 |
| 15 | 27 | Topham/Burke | Newbridge Motorsport | Aston Martin Vantage GT4 | +8.953 |
| 16 | 42 | Williams/Fielding | Steller Motorsport | Audi R8 GT4 | +8.966 |
| 17 | 3 | Valente/Benyahia | Jenson Team Rocket RJN | McLaren 570S GT4 | +9.100 |
| 18 | 90 | Marshall/Brown | Balfe Motorsport | McLaren 570S GT4 | +9.126 |
| 19 | 61 | Cowley/Moore | Academy Motorsport | Ford Mustang GT4 | +9.172 |
| 20 | 9 | Salkeld/Gordon-Colebrooke | Century Motorsport | BMW M4 GT4 | +9.282 |
| 21 | 4 | Milner/Hayek | Jenson Team Rocket RJN | McLaren 570S GT4 | +9.323 |
| 22 | 2 | Kell/Collard | Jenson Team Rocket RJN | McLaren 570S GT4 | +9.358 |
| 23 | 40 | Halstead/Stanley | Fox Motorsport | McLaren 570S GT4 | +9.788 |