Nico Rosberg was fastest for Mercedes in practice for the British Formula One Grand Prix today after rain made a mockery of the morning session.
The German, winner on the winding streets of Monaco this season, lapped the Silverstone circuit on a largely dry afternoon with a best time of one minute 32.248 seconds but was cautious afterwards.
"On one lap the car is still quick, so qualifying should be okay. But the question mark is our race speed," said Rosberg, whose team have been on pole four times in seven races.
"It could be a completely different picture on Sunday as the weather should be a lot warmer, so we don't know where we are right now compared to the others."
Australian Mark Webber, twice a winner in the last three years at Silverstone, and Red Bull team mate and championship leader Sebastian Vettel were second and third on the timesheets.
"We did a snapshot of work for tomorrow, but mostly the focus was for Sunday. I think the race will be quite tight, to be honest I don't think there's anyone charging away," commented Webber, ahead of what will be his last British Grand Prix before leaving F1 at the end of the year.
Force India's Paul Di Resta was the leading Briton in fourth place with Rosberg's team mate Lewis Hamilton, the 2008 champion, fifth fastest.
Ferrari's Felipe Massa skidded off and smashed into the tyre wall at Stowe after seven laps.
Only half of the grid had posted a timed lap in the morning practice, with most of the leading drivers remaining in their garages as the rain came down.
Australian Daniel Ricciardo, eager to show Red Bull bosses what he can do now that there is a declared vacancy at the team, was fastest in that session with a lap of 1:54.249.
That at least gave an 80,000 strong crowd some action to watch with the Red Bull, Lotus and McLaren drivers doing no more than installation laps. Lotus's Kimi Raikkonen did not bother even with that.
"Bit scary on the straight," Vettel, who leads Ferrari's Fernando Alonso by 36 points after seven of 19 races, had said over the team radio. "Quite a lot of water on the track."
"There isn't much point heading out at the moment," McLaren's Jenson Button, who has yet to stand on his home grand prix podium despite being the most experienced driver in the sport, told the BBC.
"I think we need to apologise to the fans but for us it is really wet out there and it is going to be dry at the weekend, so it is more a risk than anything else. We have some new parts and with standing water it is pretty easy to hit the wall and damage those parts."
Sauber's Nico Hulkenberg was second on the morning timesheets with Williams' Venezuelan Pastor Maldonado third and Hamilton fourth.
Caterham's French driver Charles Pic skidded off the slippery surface and into the tyre wall at Club corner, smashing the front wing, in the morning.
The bad weather meant hopes of five British drivers on track came to nothing, with Force India abandoning plans to run their simulator tester James Rossiter instead of Germany's Adrian Sutil.
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