British GP: Romain Grosjean crashes in pit lane at Silverstone
Red Bull's Pierre Gasly was the surprise pace-setter in an incident-packed first practice session at the British Grand Prix at Silverstone.
The Frenchman, who has struggled in his first season at Red Bull, went 0.476 seconds clear of Mercedes' Valtteri Bottas with a lap late in the session.
Red Bull's Max Verstappen was third and Mercedes' Lewis Hamilton fourth as several drivers had incidents.
Haas' Romain Grosjean had the worst with a crash in the pit lane and spin.
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The Frenchman, who had persuaded Haas to let him try the car in its specification from the first race of the season in a bid to understand their struggles, lost control leaving the pits for the first time because he had too much throttle on when he released the pit lane speed limit.
He spun into the inside wall, smashing his front wing, and then depositing parts of it around the track as he circulated slowly back to the pits.
After waiting in the pits for 40 minutes or so, the Franco-Swiss then had a spin at Brooklands on his first flying lap, and ended the session 19th, three places and 0.2 seconds slower than team-mate Kevin Magnussen in the current-spec car.
Bottas led the way throughout but Gasly popped into second in the closing minutes for a much-needed fillip for the Frenchman.
Verstappen also split the Mercedes drivers who had looked set to dominate before the Red Bulls upped their pace later in the session.
Bottas looked the more comfortable of the two Mercedes drivers, setting the pace in the first part of the session on the medium tyres by just under 0.3secs from Hamilton before improving on the softs.
Hamilton went off after Turn Four on his run on the soft tyres and did not improve.
Verstappen was another driver to lose control, this time at Becketts, and Ferrari's Charles Leclerc, McLaren's Lando Norris, Toro Rosso's Alexander Albon and Williams' George Russell all had 'moments' as drivers struggled with the new track surface and windy conditions. It even rained briefly at one point.
Behind Hamilton, Ferrari's Charles Leclerc and Sebastian Vettel were fifth and sixth, ahead of the Renaults of Nico Hulkenberg and Daniel Ricciardo, the Toro Rosso of Anglo-Thai Alexander Albon and McLaren's Carlos Sainz and Lando Norris.
Russell was 17th in the Williams, ahead of Alfa Romeo's Kimi Raikkonen, whose car broke down, Grosjean and the second Williams of Robert Kubica.