Nico Rosberg fastest in free practice ahead of the British Grand Prix . Mercedes driver edges out Red Bulls of Mark Webber and Sebastian Vettel . Home hope Lewis Hamilton fifth best at Silverstone . But Rosberg , who has headed the grid in three of the last four races , proved unstoppable again in the early sparring although he has some concerns for the weekend . `` Then the only question mark is our race speed . Comment:
Nico Rosberg fastest in free practice ahead of the British Grand Prix . Mercedes driver edges out Red Bulls of Mark Webber and Sebastian Vettel . Home hope Lewis Hamilton fifth best at Silverstone . Comment: