British Grand Prix: Valtteri Bottas top in second practice ahead of Lewis Hamilton
Valtteri Bottas led Lewis Hamilton in a Mercedes one-two narrowly ahead of Ferrari's Charles Leclerc in second practice at the British Grand Prix.
Bottas edged Hamilton by 0.069 seconds, with Leclerc just 0.197secs behind.
Hamilton had a scrappy day, making a series of errors and struggling to put a lap together until the key moment of his quick run in the second session.
Ferrari's Sebastian Vettel was fourth, ahead of the Red Bull of Pierre Gasly and McLaren's Lando Norris.
- Vettel on Ferrari, mistakes and the future of F1
- Hamilton unhappy with Sunday's big events clash
- F1 bosses to discuss refuelling return for 2021
Max Verstappen, winner of the last race in Austria, had a poor run on soft tyre and low fuel and was only seventh fastest.
A new track surface coupled with windy conditions at Silverstone made life difficult for the drivers, many of whom made errors and ran wide or spun.
Hamilton and Vettel both went off at the fast Becketts sweeps, while Toro Rosso's Alexander Albon and Williams' Robert Kubica had problems at Brooklands and Luffield earlier in the lap.
On the long runs, when teams simulate race pace, the Mercedes appeared to have a half-second or so advantage over Red Bull, but Ferrari's run plan meant it was hard to compare their performance.
It was a fractured day on which it was hard to read performance.
Bottas seemed to be the pace man for much of the day's running but failed to find much time on the soft tyre on low fuel, improving only by 0.03secs when he switched from the theoretically slower medium, when Leclerc found 0.8secs.
Hamilton looked out of sorts, with a series of errors and aborted laps affecting his running until finally finding some pace - but still not able to quite match Bottas.
Ferrari were off the pace for much of the day, only for Leclerc to pull out a strong lap time on his low-fuel run.
And Red Bull, after setting the pace with Gasly in the morning session, struggled in the afternoon.
And on the longer runs, both Verstappen and Leclerc ran into severe wear on the left front tyre, which looks like it will be the limiting factor in the race.
Behind the big three teams, Norris continued to impress, just a couple of days after McLaren confirmed that they had taken up their contractual option on the 19-year-old rookie for 2020.
His team-mate Carlos Sainz was eighth quickest, ahead of Toro Rosso's Alexander Albon and Racing Point's Sergio Perez.
Renault's Daniel Ricciardo had a difficult day. He was only 14th fastest, just ahead of team-mate Nico Hulkenberg, and stopped midway through the session with an engine failure.
"It's been quite windy, quite gusty out there," said Hamilton. "It hasn't been the easiest of days, but we were up there nonetheless, and it looks like we'll be in the fight.
"The new track surface is better on the straights, especially between Turn 4 and Turn 6 where it was pretty bad before. It's still bumpy on the exit of Turn 7 and towards Copse, but after that it's nice and smooth through Maggotts and Becketts and down the Hanger straight.
"The asphalt is very smooth which makes it tricky to get the tyres to work. They're in and out of the window, and the gusty winds didn't make it easy. I was struggling with the rear end and went off a few times, but Valtteri seemed much more comfortable in the car, so we are going to dig deep tonight trying to figure out what the issue is and how we can solve it."
Vettel added: "We tried some stuff which maybe makes it a bit difficult to read. Mercedes look very, very strong and then I think it is very close between us and Red Bull."