The Monaco-born driver lapped the Silverstone circuit on an overcast, gusty and much cooler afternoon than Friday with a best time of one minute 25.498 seconds.
McLaren’s Formula One championship leader Oscar Piastri was second quickest, 0.068 seconds slower, with Red Bull’s Max Verstappen third.
The session was twice red-flagged, once when Oliver Bearman’s Haas shed some bodywork and in the final seconds when Gabriel Bortoleto spun on a kerb and bounced across the grass with the car’s front left suspension smashed.
The final stoppage put paid to anyone trying to improve on Leclerc’s time, including Ferrari’s Lewis Hamilton who ended up only 11th.
Hamilton had been quicker than Leclerc in the first two sectors before aborting the final one after the red flags were waved as a result of Bearman’s debris on track.
McLaren’s Lando Norris, 15 points adrift of Piastri after 11 of 24 rounds, was fourth fastest with Red Bull’s Yuki Tsunoda fifth.
Bearman, who ended up sixth, crashed in a bizarre accident at the end while entering the pitlane — smashing the nose and front wing when he hit the barriers and blaming cold brakes.
Alex Albon was seventh for Williams, ahead of Mercedes’ George Russell, Racing Bulls’ Isack Hadjar and teammate Liam Lawson completing the top 10.
Aston Martin said neither of their drivers had managed to do a representative lap on the fastest soft tyre due to the red flags.
Qualifying for Sunday’s race, Hamilton’s first at home in Ferrari colours, follows later in the afternoon.
Seven-times world champion Hamilton, a record nine times British GP winner, won last year for Mercedes.
--Reuters--