Lewis Hamilton fastest in British Grand first practice
Lewis Hamilton led Valtteri Bottas in a Mercedes one-two ahead of Ferrari's Sebastian Vettel in first practice at the British Grand Prix.
Hamilton was 0.367 seconds clear of the Finn and 0.511secs ahead of Vettel, who leads the championship by one point.
Haas driver Romain Grosjean had a heavy crash at the 180mph first corner after failing to close a DRS overtaking aid.
The Frenchman apologised to his team, saying that a bump on entry had caused him to miss the DRS button.
"The car is destroyed," Grosjean said over the radio. "I'm very, very sorry. I think it was the bump. I missed the button."
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It was the latest in a series of errors this season by Grosjean, whose future at the team beyond 2018 is in doubt as a result.
Under blue summer skies, and warm temperatures, Mercedes consolidated their status as favourites for this weekend, and the team need a strong result after their double retirement in Austria last Sunday.
Mercedes have changed Bottas' engine for this weekend because the one in the car in Austria went through what is called a 'heat soak event' when he retired as a result of a hydraulic failure.
The Finn will not receive a grid penalty and they hope to use the Austria engine again at the next race in Germany, but has now used up his allocation of engines for the season, which means if Mercedes introduce an upgrade later in the year, he will have to weigh its improvement against the grid penalty he would receive for using it.
Hamilton complained about bumps on the resurfaced track, and said over the radio during the virtual safety car period following Grosjean's crash that he was unhappy with the car. However, he stayed out and set his fastest time.
Ferrari's pace was encouraging for them in the context of what has been their general lack of pace on Fridays this season, before they bounce back to the front on Saturdays.
Red Bull's Daniel Ricciardo was fourth, ahead of Ferrari's Kimi Raikkonen, who had a spin at Brooklands, and the second Red Bull of Max Verstappen, who stopped on the pit straight with a gearbox problem with three minutes to go in the session.
Grosjean was seventh fastest with the time he set before his crash, ahead of the Force Indias of Sergio Perez and Esteban Ocon, and the Williams of Lance Stroll.
Grosjean's team-mate Kevin Magnussen was 14th but has to report to the stewards after the session after being accused of dangerous driving in an incident with McLaren's Fernando Alonso.
The Dane appeared to veer at Alonso's car on the Wellington Straight towards Turn Six, Brooklands, after the two tripped over each other through the first corner, Abbey, as Alonso was on a slow lap and Magnussen a fast one.
Alonso ended the session 15th fastest on McLaren's first weekend since the departure of racing director Eric Boullier and the introduction of a restructured management team.