Silverstone, Northamptonshire - Formula One world champion Lewis Hamilton laid down a marker with the fastest lap in Friday's first practice for his home British Grand Prix, with Mercedes one-two at the top of the timesheets.
Hamilton, who will be chasing his fifth consecutive Silverstone victory on Sunday and sixth in total at the former Second World War airfield, posted a best time of 1m27.487s - more than half a second faster than Ferrari's Sebastian Vettel, who leads fellow four-times champion Hamilton by a point in the standings after nine of 21 races with three wins apiece.
Hamilton's Finnish team-mate Valtteri Bottas, with a new engine in his car after last weekend's retirement in Austria, was second fastest but 0.367 off the pace; Daniel Ricciardo was fourth for Red Bull with Ferrari's Kimi Raikkonen fifth and Max Verstappen, winner in Austria for Red Bull, sixth - after ending the session early when he was told to stop the car.
Haas's Romain Grosjean had a heavy crash at the first corner after failing to close the drag reduction system. Romain, who was unhurt in the impact, said over the radio: "The car is destroyed. I'm very, very sorry guys. I think it was the bump. I missed the button."
Team boss Guenther Steiner said Grosjean, who finished fourth in Austria, would take no further part in the day's track action.
"We need to change the chassis so he will not be going out for FP2," he said.
Grosjean's team-ate Kevin Magnussen and McLaren's Fernando Alonso were called in to see the stewards for a "potentially dangerous manoeuvre" after an incident between them early on, when Alonso reported over the radio: "Magnussen tried to hit me two times - in one and three - very dangerous."
1 Lewis Hamilton (Mercedes) 1m27.487
2 Valtteri Bottas (Mercedes) +0.367
3 Sebastian Vettel (Ferrari) +0.511
4 Daniel Ricciardo (Red Bull) +0.657
5 Kimi Raikkonen (Ferrari) +0.791
6 Max Verstappen (Red Bull) +0.838
7 Romain Grosjean (Haas) +1.865
8 Sergio Perez (Force India) +2.325
9 Esteban Ocon (Force India) +2.328
10 Lance Stroll Williams +2.391
12 Marcus Ericsson (Sauber) +2.455
13 Pierre Gasly (Toro Rosso) +2.517
14 Charles Leclerc (Sauber) +2.540
15 Kevin Magnussen (Haas) +2.578
16 Fernando Alonso (McLaren) +2.835
17 Carlos Sainz (Renault) +2.871
18 Stoffel Vandoorne (McLaren) +2.929
19 Nico Hulkenberg (Renault) +3.214
20 Brendon Hartley (Toro Rosso) +3.262
21 Sergey Sirotkin (Williams) +3.530