British Grand Prix 2014: Lewis Hamilton fastest in second practice but sees his Mercedes suffer more problems

Briton's car ground to a halt with 30 minutes remaining

World Championship leader Nico Rosberg was the fastest in practice (Getty Images)

Lewis Hamilton may have finished top of the timesheet in practice for Sunday's British Grand Prix but the home hero was left to ponder the latest failure to his Mercedes.

Two retirements this season - in the opening race in Australia and again in Canada last month - have cost Hamilton dear in his clash for the Formula One world title with team-mate Nico Rosberg.

The 29-year-old heads into his home race 29 points adrift of Rosberg and in dire need of a result to quell the German's forward momentum after a run of three grands prix in which he has heavily outscored the Briton.

But at a time when Hamilton was beginning to flex his muscles around Silverstone by posting the fastest lap on the quicker of Pirelli's two tyre compounds for this weekend - the medium - his car ground to a halt with 30 of the 90 minutes remaining.

The collective groan from the majority of the 70,000-strong crowd at the Northamptonshire venue was a deep one as Hamilton clambered out of the cockpit of a car that had stopped between turns three and four - The Loop and Aintree respectively.

It was proof again Mercedes are far from bulletproof in a season they have so far dominated, although Hamilton must be wondering 'why me?' as Rosberg has avoided such issues.

The 29-year-old has so far finished in the top two in all eight races to eke out his margin over Hamilton, although he did suffer the same loss of ERS (energy recovery system) in Montreal.

However, whereas Rosberg managed to nurse his car to the runner-up spot, Hamilton's failure resulted in a loss of the rear brakes, and with it retirement.

Hamilton will obviously now be hoping he has no more issues over the remaining two days if he is to eat into Rosberg's advantage.

At least there will be some satisfaction in finishing 0.228 seconds ahead of Rosberg at the end of the two Friday sessions, with his best lap a one minute 34.508secs.

Again, as in FP1, only Fernando Alonso finished within a second of the dominant Mercedes duo, with the Ferrari star 0.736secs adrift of Hamilton.

Red Bull pairing Daniel Ricciardo and Sebastian Vettel were fourth and fifth quickest respectively, just over a second off the pace, with Williams' Valtteri Bottas 1.5secs down in sixth.

Bottas, however, concluded a troubled day for Williams with a bizarre bang underneath the engine cover that exploded through the bodywork when the Finn was out on track five minutes from the end.

Bottas had returned to his car following a first session for Susie Wolff that unfortunately ended after just 20 minutes with an engine failure due to an oil pressure problem inside the Mercedes power unit.

As the first woman in 22 years to take part in an F1 weekend, and only the sixth overall, Wolff's day in the spotlight resulted in the Scot managing one timed lap before pulling off track.

As for team-mate Felipe Massa, the Brazilian spun off at Stowe and crashed heavily into a barrier, only for his team to perform wonders by getting him back on track for FP2, at the end of which he finished 11th, just over two seconds back.

McLaren's Jenson Button and Kevin Magnussen were seventh and eight best respectively, both 1.7secs down, with Marussia's Max Chilton in 21st and 4.7secs in arrears.

PA