Felipe Massa capitalised on the fast-improving track conditions to go fastest in second practice for the British Grand Prix, edging out Nico Rosberg and Kamui Kobayashi in an unusual top three.
Heavy rain fell moments before the green light, meaning the first timed lap of the session took over 50 minutes, with Jaime Alguersuari clocking a 2:04.096 on the gull wet tyres, but the times would quickly tumble as more and more drivers decided the track was ready for some serious running.
In the space of ten minutes, the Spaniard had taken nearly ten seconds off the benchmark time to lead teammate Sebastien Buemi and Michael Schumacher before Adrian Sutil leapfrogged the Toro Rosso pair with a 1:53.676.
The big guns didn't venture out until the final 20 minutes and Mark Webber moved to the top with a 1:53.537 on his second flying lap before improving by almost a second on his fourth. The intermediates were now clearly the tyres to be on.
Jenson Button proved that in the final two minutes by smashing the fastest first sector time although he couldn't maintain the pace in the rest of the lap. Schumacher could as he set a 1:52.325 but several drivers behind him were also laying claim to the fastest time.
After Sutil had briefly gone quickest, Nico Rosberg demoted him with a 1:50.744 for Mercedes, with Kamui Kobayashi slotting into second. Home favourites Hamilton and Button also put on a late charge to go third and fourth.
But the man on the move was Massa, who put in a 1:49.777 on his final lap to finish the day on top of the timesheets. This pushed Rosberg and Kobayashi down to second and third ahead of the two McLarens with Adrian Sutil completing the top six.
Paul di Resta also showed strong pace in the wet to go seventh while Rubens Barrichello and Sergio Perez got into the top ten in the dying moments, a leaderboard rounded out by early pacesetter Sebastien Buemi.
Vitaly Petrov was next up while Michael Schumacher was the fastest driver on the full wet tyres in 12th. Heikki Kovalainen was up in 13th for Lotus, ahead of Mark Webber who chose not to risk his car in the final five minutes. Teammate Sebastian Vettel did likewise and finished down in 18th having only completed four laps.
The two Red Bulls were separated by Fernando Alonso's Ferrari, Nick Heidfeld's Renault and Jaime Alguersuari's Toro Rosso who couldn't keep up as the times rapidly improved late on.
Jerome D'Ambrosio was the fastest Virgin in 19th ahead of Pastor Maldonado and Jarno Trulli with Timo Glock 22nd in the second MVR-02. The two HRTs were slowest of all, with Daniel Ricciardo impressing to outpace teammate Vitantonio Liuzzi.