Juan Pablo Montoya gave Williams the perfect leaving present by claiming their first victory of the season after taking advantage of changeable conditions in the Brazilian Grand Prix at Interlagos.

The Colombian, in his last race for Williams before moving to McLaren, came out on top after showers early in the race shuffled the running order.

He kept his head to end the season on a high note, denying 2005 team-mate Kimi Raikkonen the win by just one second after 71 laps, despite heavy late pressure from the Finn.

Rubens Barrichello, who started on pole position, saw his dreams of a home victory shattered by the early rain, although he at least finished for the first time in 10 attempts in Brazil, claiming third.

Fernando Alonso led early on but he ended the race fourth for Renault.

World champion Michael Schumacher overcame the handicap of starting 18th to take points for seventh while brother Ralf, in his final race for Williams, was fifth.

BAR secured second place in the constructors' championship but the season ended on a disappointing note for Jenson Button, who retired early on with mechanical trouble. Takuma Sato scored their only points with sixth.

Felipe Massa, on home ground, scored the final point for Sauber while David Coulthard was 11th for McLaren.

Rain for 45 minutes meant difficult track conditions allowed Raikkonen to power his McLaren past Barrichello's Ferrari on the opening lap.

Michael Schumacher started 18th after a heavy crash in practice but was 10th at the end of lap one.

His charge through the field was interrupted when he spun at turn two on the second lap though.

Barrichello got back in front on lap four, easing past Raikkonen down the start-finish straight.

Button's podium hopes were ended on the same lap when he pulled his BAR on to the grass with smoke pouring from his Honda engine, as it had done on the starting grid. That promoted Montoya's Williams to third.

Montoya and Raikkonen took their first pit stop together and the Colombian was able to edge ahead into second.

The track was dry by lap eight, playing into the hands of Alonso, who had bucked the general trend by opting for slick tyres from the start.

Barrichello's difficulties as the track was drying left him down in sixth.

Nick Heidfeld's Jordan broke down on lap 18 as Alonso pitted for the first time and Montoya took over the lead.

On lap 25, Jaguar's last race in Formula One was marked by an embarrassing incident.

Mark Webber moved to overtake Christian Klien but the Austrian appeared oblivious and turned in on his team-mate, who was eliminated on the spot.

Showers began on lap 30 and despite being slower than Raikkonen prior to the second stops, Montoya was able to extend his lead afterwards.

On lap 33 Sato ran wide going into turn one on a slippery track to allow Barrichello through to fifth.

The final round of stops saw Alonso lose out, dropping down to fourth place as Barrichello sneaked ahead.

Raikkonen made his final visit to pit lane on lap 55, five later than Montoya, after clawing back some of the deficit to Montoya, but it was not enough to put him ahead.

He was quicker than Montoya after the stops though and moved to within a second to set up an exciting battle for victory, which the Colombian held on to take.