SILVERSTONE - Lewis Hamilton remained calm despite another setback with his car on Friday after he topped the times in second practice for this weekend's British Grand Prix.

The 29-year-old Briton, who is bidding to add a second home triumph to his victory of 2008, clocked the fastest lap of the afternoon, but was then left stranded on track with engine problems. He had outpaced Mercedes team-mate and championship leader German Nico Rosberg with a best lap of 1min 34.508sec to emerge fastest by 0.228sec on a warm and blustery day at Silverstone. "I'm not frustrated," said Hamilton, who missed the last half hour of the session. "You know, it just happened, but, I just don't know why it keeps happening to my car so much."

In a later comment on his Twitter account, he added: "When you step back and look, things are positive - it's not the race and we can learn from this." Hamilton lies second in the title race, 29 points behind Rosberg and has said he needs to win on Sunday to regain momentum in their duel for the crown. He has twice suffered mechanical failures and retirements in races, but Rosberg has finished every race in the leading two. Two-time champion Fernando Alonso of Spain, steered his Ferrari into third fastest, seven seconds down on the pace-setter, ahead of the two Red Bulls of Australian Daniel Ricciardo and German defending four-time champion Sebastian Vettel. They were both more than a second behind on one lap pace but showed improvements in relative competitive speed on the long runs in the latter stages of the long afternoon session.

Hamilton seemed to suffer a serious engine problem an hour into the 90-minutes session when he stopped out on the circuit. "Engine stopped," he told the team by radio. "Says engine kill, no shifting." Hamilton managed only 14 completed laps in the session compared to Rosberg's 35, but will have access to the championship leader's data after the session. Rosberg leads Hamilton by 29 points in the title race.

Finn Valtteri Bottas was sixth fastest for Williams - having missed the morning session when his car was run by Susie Wolff, the first woman to take part in a Grand Prix for 22 years - ahead of Briton Jenson Button in the leading McLaren. Danish rookie Kevin Magnussen was eighth fastest in the second McLaren ahead of Finn Kimi Raikkonen of Ferrari and 10th placed Frenchman Jean-Eric Vergne of Toro Rosso.

In a day of many incidents, the afternoon saw Swedish rookie Marcus Ericsson of Caterham and Vergne running off track and Bottas surviving an engine explosion after pulling his car into the Williams garage.