Nico Rosberg set the practice pace yet again in the Saturday morning session at Silverstone, this time leading his teammate Kazuki Nakajima in a Williams one-two.
Their late surge pushed Jarno Trulli back to third, with yesterday's pace-setter Sebastian Vettel fourth for Red Bull.
Jenson Button's low-key weekend continued as the championship leader managed only 12th position, one place behind fellow home driver Lewis Hamilton's McLaren.
With the track damp at the beginning of the session following early rain, it was a long time before anyone came out for a serious run.
Renault's Nelson Piquet proved the track was ready for slicks after 23 minutes, and from then on the times tumbled and the positions changed at a frenetic rate as the circuit conditions improved with every minute.
Rosberg took several turns on top as he repeatedly grabbed first position back again after being usurped, with his team-mate Nakajima, both Toyotas, Toro Rosso's Sebastien Bourdais and both Red Bulls also featuring in first place at times before the soft tire qualifying simulation runs began on the now bone dry track with ten minutes to go.
It was Felipe Massa (Ferrari) who was first to beat Vettel's hard tire benchmark, despite running wide out of Woodcote. The Ferrari then dropped from first to fourth in a matter of seconds as Trulli and the two Williams jumped into the top three positions.
Both Rosberg and Nakajima had time for second flying laps too, and for a few moments it looked like the Japanese driver might emerge fastest from a Formula 1 practice session for the first time as he pushed Trulli off the top spot.
But Rosberg was on a typical last minute charge, and he duly beat his team-mate by 0.203s.
Behind Trulli and Vettel, the two Ferraris completed the top six, ahead of Timo Glock, who escaped a wild trip across the grass at Becketts late in the session.
Fernando Alonso was eighth for Renault, ahead of Red Bull's Mark Webber and Rubens Barrichello in the quicker of the two Brawns.
Force India did not maintain its top three form from Friday, but both Adrian Sutil and Giancarlo Fisichella managed to beat the BMWs, Sebastien Buemi and McLaren's Heikki Kovalainen.TIMES:
Pos Driver Team Time Laps
1. Rosberg Williams-Toyota (B) 1:18.899 20
2. Nakajima Williams-Toyota (B) 1:19.102 + 0.203 19
3. Trulli Toyota (B) 1:19.125 + 0.226 15
4. Vettel Red Bull-Renault (B) 1:19.371 + 0.472 15
5. Massa Ferrari (B) 1:19.596 + 0.697 19
6. Raikkonen Ferrari (B) 1:19.855 + 0.956 13
7. Glock Toyota (B) 1:19.868 + 0.969 19
8. Alonso Renault (B) 1:19.917 + 1.018 14
9. Webber Red Bull-Renault (B) 1:19.946 + 1.047 15
10. Barrichello Brawn GP-Mercedes (B) 1:20.028 + 1.129 14
11. Hamilton McLaren-Mercedes (B) 1:20.048 + 1.149 16
12. Button Brawn GP-Mercedes (B) 1:20.157 + 1.258 17
13. Piquet Renault (B) 1:20.232 + 1.333 18
14. Bourdais Toro Rosso-Ferrari (B) 1:20.459 + 1.560 17
15. Sutil Force India-Mercedes (B) 1:20.548 + 1.649 15
16. Fisichella Force India-Mercedes (B) 1:20.572 + 1.673 17
17. Kovalainen McLaren-Mercedes (B) 1:20.638 + 1.739 18
18. Heidfeld BMW Sauber (B) 1:20.696 + 1.797 20
19. Buemi Toro Rosso-Ferrari (B) 1:21.024 + 2.125 11
20. Kubica BMW Sauber (B) 1:21.039 + 2.140 13
All timing unofficial