Valtteri Bottas fastest in first practice, Lewis Hamilton second
Valtteri Bottas set the pace as Mercedes dominated first practice at the British Grand Prix.
The Finn, who won in Austria on Sunday, was 0.078 seconds quicker than team-mate Lewis Hamilton, as the two swapped fastest times through the session.
Hamilton's title rival Sebastian Vettel was sixth quickest, 1.411secs off the pace after a big spin at Becketts and a trip over the kerbs at Village.
Hamilton is 20 points behind Vettel with Bottas a further 15 points behind.
Red Bull were Mercedes' closest rivals out on the track on Friday morning as the weekend started under grey skies, with a chill wind and temperatures at only 15-16C.
Max Verstappen was third fastest, 0.498secs off the pace and 0.338secs ahead of team-mate Daniel Ricciardo, with Kimi Raikkonen the fastest Ferrari in fifth.
But Mercedes' superiority on this high-speed circuit was underlined by the fact they set their fastest times on the soft tyre, whereas their rivals were on the super-soft.
There were some encouraging signs for McLaren, as Fernando Alonso set the eighth-fastest time behind Toro Rosso's Daniil Kvyat, and team-mate Stoffel Vandoorne only 0.048secs behind the Spaniard in 10th.
Alonso already knows he will have at least a five-place grid penalty as a result of using too many engine parts and Honda has said more are likely to be on the way.
The McLarens were separated by Williams driver Felipe Massa in ninth, six places and 0.685secs quicker than team-mate Lance Stroll.
Vettel's session was full of incident. He began it by trying out the latest cockpit head-protection system, known as the 'shield', a clear screen in front of the driver aimed at deflecting potentially dangerous objects from his head.
The four-time champion did only one lap running the device and then had a big spin at the final right-hander in the Becketts section of sweeps on his first run when the rear snapped away from him mid-corner.
He then ran wide on the exit of Vale, the fourth corner, and bounced over the kerbs.
Adding to the impression that the Ferrari may be lacking rear grip so far this weekend, Raikkonen had a 'tank-slapper' out of Brooklands midway through the session, narrowly avoiding losing the car after the rear snapped one way and then the other.
It was a difficult session for Renault, with Jolyon Palmer down in 18th place, 3.344secs off the pace and one place and 0.279secs behind team-mate Nico Hulkenberg.