Marc Marquez dominated the opening practice session for MotoGP's British Grand Prix at Silverstone. The reigning world champion, whose 2014 winning streak finally ended in the Czech Republic a fortnight ago, was on top throughout Friday morning's session. Marquez generally kept his Honda between half a second and a second clear of his rivals, and ended the 45 minutes with a 0.661-second gap back to second-placed Andrea Iannone. There was a scare for the championship leader, though, as he had to slew off the road at Vale when he nearly clipped Pol Espargaro's Tech 3 Yamaha on his final flying lap. Until that incident, Marquez had looked set to go even quicker on that run. Iannone thrust his Pramac Ducati into second ahead of Andrea Dovizioso's factory machine in the closing seconds. Alvaro Bautista showed better form than of late to go fourth for Gresini, followed by Aleix Espargaro and Stefan Bradl. Marquez's usual rivals were a long way down. Yamaha duo Jorge Lorenzo and Valentino Rossi were only seventh and eighth, with Brno winner Dani Pedrosa back in 10th on the second works Honda, 1.1s slower than his team-mate. It was a tough start for home rider Michael Laverty and the British Paul Bird Motorsport team. Laverty sat out much of the early running in the pits, and then parked trackside with smoke pouring from his bike soon after making it out.