Silverstone: Nico Rosberg stamped his authority on Friday`s preparations for this weekend`s British Grand Prix by clocking the fastest time in both free practice sessions while Mercedes team-mate Lewis Hamilton struggled to find any rhythm.
The 30-year-old German clocked a best time of one minute and 34.155 seconds in the afternoon to wind up three-tenths of a second ahead of the two Ferraris of Finn Kimi Raikkonen and four-time champion Sebastian Vettel of Germany.
Hamilton was a further tenth of a second adrift back in fourth after a ragged day that saw him fighting for balance and pace in a gusty wind and intermittent hot conditions in front of his home fans at Silverstone.
The series leader and defending two-time champion had struggled to match Rosberg, who overcame a loss of hydraulics during the morning, throughout the day.
"The car`s all over the place - I can`t go any faster than I am right now," a frustrated Hamilton told the team with 15 minutes remaining.
Russian Daniil Kvyat was fifth for Red Bull ahead of his Australian team-mate Daniel Ricciardo, Dutch teenager Jos Verstappen of Toro Rosso and German Nico Hulkenberg of Force India.
Spaniard Carlos Sainz was ninth in the second Toro Rosso and Brazilian Felipe Massa 10th for Williams while the two McLaren-Hondas of world champions Spaniard Fernando Alonso and Briton Jenson Button were 15th and 17th respectively.
The session was twice interrupted by red flags, when Frenchman Romain Grosjean of Lotus and later Spaniard Roberto Merhi of Manor lost control and went off at Luffield, a corner that also claimed Alonso who ran off at the same place.
Nobody was injured in any of these off-track excursions on a day when Rosberg`s meticulous approach to his job paid dividends in difficult, hot and testing conditions, the air temperature hovering around 24 degrees Celsius and the track touching 40 degrees.