Alonso fastest in final practice - Britain

Red Bull's Mark Webber took second, ahead of McLaren's Heikki Kovalainen and the impressive Sebastian Vettel (Toro Rosso).

With a morning rain shower having doused the circuit prior to practice, times were initially over 15 seconds slower than yesterday's as drivers toyed with extreme wet tyres before switching to 'intermediates' as the circuit began to dry.

Inevitably this meant that the order changed frenetically throughout the session, as track conditions improved with every minute.

With just under 20 minutes to go, Nick Heidfeld became the first man to experiment with dry weather tyres, and his decision proved to be a wise one, as the BMW driver immediately beat Felipe Massa's previous benchmark by four seconds, and then found another two seconds on his next lap.

Heidfeld's times prompted a wholesale switch to 'slicks', and an even more chaotic scene on the timing screens in the remaining quarter of an hour, as the top spot swapped between Alonso, Timo Glock (Toyota) and Kimi Raikkonen (Ferrari) in quick succession, before Webber hit the front with nine minutes remaining.

In the closing minutes many of the field decided that conditions were now good enough to try the softer dry tyre. Kovalainen was the first to do so and produced a 1:21.266 lap to beat Webber by just over half a second.

Many others followed Kovalainen's example, but his time remained the benchmark until Alonso lapped in 1:20.740 with his last lap. Moments later, Webber leaped back up to second, 0.248 seconds slower than Alonso, while Vettel came within 0.011 seconds of beating Kovalainen to third.

Lewis Hamilton completed the top five in his McLaren, with the Ferraris back in ninth (Raikkonen) and 12th (Felipe Massa).

Despite the tricky conditions causing numerous slides, most drivers managed to stay out of trouble. Having crashed on the exit of the Abbey chicane yesterday, Kazuki Nakajima spun his Williams on the entry to the corner this morning, but rejoined without drama. Jarno Trulli also had a harmless spin at Club in his Toyota.

David Coulthard had to sit out much of the session due to a technical problem on his Red Bull, and was stranded in the garage when the circuit dried out. That left him at the tail of the order and 10 seconds off the pace as the rest of the field improved on slicks.

Pos  Driver        Team                     Time              Laps
 1.  Alonso        Renault             (B)  1:20.740            16
 2.  Webber        Red Bull-Renault    (B)  1:20.988 +  0.248   18
 3.  Kovalainen    McLaren-Mercedes    (B)  1:21.266 +  0.526   14
 4.  Vettel        Toro Rosso-Ferrari  (B)  1:21.277 +  0.537   19
 5.  Hamilton      McLaren-Mercedes    (B)  1:21.668 +  0.928   14
 6.  Piquet        Renault             (B)  1:21.786 +  1.046   14
 7.  Bourdais      Toro Rosso-Ferrari  (B)  1:22.059 +  1.319   21
 8.  Glock         Toyota              (B)  1:22.183 +  1.443   21
 9.  Raikkonen     Ferrari             (B)  1:22.355 +  1.615   20
10.  Barrichello   Honda               (B)  1:22.387 +  1.647   17
11.  Button        Honda               (B)  1:22.440 +  1.700   19
12.  Massa         Ferrari             (B)  1:22.461 +  1.721   20
13.  Rosberg       Williams-Toyota     (B)  1:22.544 +  1.804   18
14.  Trulli        Toyota              (B)  1:22.556 +  1.816   20
15.  Heidfeld      BMW Sauber          (B)  1:22.916 +  2.176   22
16.  Nakajima      Williams-Toyota     (B)  1:23.028 +  2.288   17
17.  Sutil         Force India-Ferrari (B)  1:23.049 +  2.309   22
18.  Fisichella    Force India-Ferrari (B)  1:23.112 +  2.372   21
19.  Kubica        BMW Sauber          (B)  1:23.282 +  2.542   20
20.  Coulthard     Red Bull-Renault    (B)  1:32.119 + 11.379    6

All timing unofficial