Mikkel Grundtvig took his second GB3 Championship win of the season at Donington Park, winning Race 3 in Leicestershire for the second time this season.
The Danish driver started on pole, ahead of Reema Juffali and Tommy Smith in the Douglas Motorsport cars.
Bryce Aron was squeezed out on the exit of Goddards, as Reece Ushijima pitted with a rear puncture at the end of the first lap to rule himself out of the fight for second place in the championship.
Christian Mansell ran wide on the exit of the Old Hairpin and just avoided Bart Horsten as he rejoined on Lap 3.
Roman Bilinski moved past Tommy Smith at the Melbourne Hairpin a lap later, with Ushijima setting the fastest lap on his return from the pits.
James Hedley smacked the kerbs at the Esses and ran into the gravel as he tried to defend from Ayrton Simmons.
Javier Sagrera retired from the race after a collision with Christian Mansell at McLeans, as the Australian’s chances of taking second in the standings further diminished.
Juffali lost four places under pressure from Tom Lebbon, Roberto Faria, Johnathan Browne and Simmons.
Simmons then managed to get past Sebastian Alvarez, battling through what looked to be minor front wing damage.
Faria, Alvarez and Zak O’Sullivan had all moved up ten positions by the end of Lap 8, with O’Sullivan having to defend from Juffali at Redgate on Lap 9.
Juffali then suffered a five-second time penalty for exceeding track limits, as Ushijima again set the fastest lap in the closing stages.
O’Sullivan and Roman Bilinski both moved past Simmons at the Melbourne Hairpin on the penultimate lap, with Branden Oxley having lost his front wing.
Grundtvig held on for his second win of the season, ahead of Alex Fores and Frederick Lubin.
Roberto Faria took fourth ahead of Tom Lebbon and Johnathan Browne.
Sebastian Alvarez was seventh, leading O’Sullivan, Bilinski and Ayrton Simmons, the latter taking second in the Drivers’ Championship.
2021 Donington Park Race 3 Results:
| Pos. | No. | Name | Nat. | Team | Laps/Gap |
| 1 | 43 | Mikkel Grundtvig | DEN | Fortec Motorsport | 12 laps |
| 2 | 90 | Alex Fores | GBR | Chris Dittmann Racing | +0.958s |
| 3 | 78 | Frederick Lubin | GBR | Arden Motorsport | +2.265s |
| 4 | 7 | Roberto Faria | BRA | Fortec Motorsport | +6.571s |
| 5 | 34 | Tom Lebbon | GBR | Elite Motorsport | +9.299s |
| 6 | 5 | Johnathan Browne | ROI | Hillspeed | +9.576s |
| 7 | 12 | Sebastian Alvarez | MEX | Hitech GP | +9.931s |
| 8 | 51 | Zak O’Sullivan | GBR | Carlin | +10.974s |
| 9 | 4 | Roman Bilinski | POL | Arden Motorsport | +11.840s |
| 10 | 18 | Ayrton Simmons | GBR | Chris Dittmann Racing | +16.352s |
| 11 | 50 | Bart Horsten | AUS | Hitech GP | +17.030s |
| 12 | 16 | Eduardo Coseteng | FIL | Fortec Motorsport | +17.401s |
| 13 | 67 | James Hedley | GBR | Elite Motorsport | +19.553s |
| 14 | 23 | Bryce Aron | USA | Carlin | +20.002s |
| 15 | 10 | Reema Juffali | SAU | Douglas Motorsport | +20.445s |
| 16 | 21 | Christian Mansell | AUS | Carlin | +20.589s |
| 17 | 33 | Flynn Jackes | AUS | Hillspeed | +21.613s |
| 18 | 55 | Tommy Smith | AUS | Douglas Motorsport | +23.615s |
| 19 | 68 | Branden Oxley | GBR | Chris Dittmann Racing | +25.191s |
| 20 | 13 | Reece Ushijima | JPN | Hitech GP | +56.389s |
| 21 | 3 | Javier Sagrera | SPA | Elite Motorsport | DNF |