Nico Rosberg and Kazuki Nakajima gave Williams a one-two in the second free practice session for the Spanish Grand Prix at Catalunya.
The team held on to its commanding position despite pace-setter Rosberg pulling off the road with a mechanical problem on his final lap of the afternoon.
Local hero Fernando Alonso buoyed the Barcelona crowd with third place, with Rubens Barrichello and Jenson Button taking fourth and sixth for Brawn, split by Mark Webber's Red Bull.
Williams led the way for the majority of the session.
After the early flurry of quick times had ended with Renault's Nelson Piquet at the head of the field following a soft-tire run, Nakajima established himself in first place at the 25-minute mark. He was briefly deposed by Sebastian Vettel's Red Bull, but only for a few minutes before returning to first place.
When Nakajima was finally beaten with a quarter of an hour remaining, it was his teammate Rosberg who took the position with a time of 1m21.588s – 0.152sec quicker than his Japanese teammate.
Rosberg looked set to improve further on his last flying lap, only for the car to grind to a halt on the approach to Turn 10.
Alonso grabbed third late on, ahead of the Red Bulls and Brawns.
Following his initial strong form, Piquet had a difficult session. He slid through the gravel at Campsa and brushed the tire wall, requiring assistance from the marshals to rejoin. Luckily his Renault was undamaged, but he paid a second visit to the gravel on his return to the track – this time spinning at Turn 3.
Despite these incidents, the Brazilian still ended the session in eighth.
Force India's Adrian Sutil missed the entire session due to a fuel cell problem, while Sebastien Buemi had to park his Toro Rosso with smoke coming from its brakes on its out-lap at the start of the afternoon, but was able to rejoin after repairs and take ninth ahead of Kimi Raikkonen's Ferrari.
After its strong challenge for the top spot in the morning, Toyota appeared to run a more conservative program this afternoon. Timo Glock and Jarno Trulli were slowest of those running in the session, but completed nearly 50 laps each.RESULTS:
Pos Driver Team Time Laps
1. Rosberg Williams-Toyota (B) 1:21.588 43
2. Nakajima Williams-Toyota (B) 1:21.740 + 0.152 40
3. Alonso Renault (B) 1:21.781 + 0.193 36
4. Barrichello Brawn-Mercedes (B) 1:21.843 + 0.255 39
5. Webber Red Bull-Renault (B) 1:22.027 + 0.439 37
6. Button Brawn-Mercedes (B) 1:22.052 + 0.464 35
7. Vettel Red Bull-Renault (B) 1:22.082 + 0.494 45
8. Piquet Renault (B) 1:22.349 + 0.761 26
9. Buemi Toro Rosso-Ferrari (B) 1:22.571 + 0.983 17
10. Raikkonen Ferrari (B) 1:22.599 + 1.011 40
11. Bourdais Toro Rosso-Ferrari (B) 1:22.615 + 1.027 30
12. Fisichella Force India-Mercedes (B) 1:22.670 + 1.082 32
13. Hamilton McLaren-Mercedes (B) 1:22.809 + 1.221 31
14. Kovalainen McLaren-Mercedes (B) 1:22.876 + 1.288 29
15. Massa Ferrari (B) 1:22.878 + 1.290 35
16. Kubica BMW-Sauber (B) 1:22.948 + 1.360 40
17. Heidfeld BMW-Sauber (B) 1:23.173 + 1.585 39
18. Glock Toyota (B) 1:23.360 + 1.772 46
19. Trulli Toyota (B) 1:23.623 + 2.035 47
20. Sutil Force India-Mercedes (B)
All Timing Unofficial