Mark Webber made it a phenomenal 12 pole positions from 13 races this season for Red Bull Racing as he grabbed top spot for tomorrow's Belgian Grand Prix.

Following a tricky qualifying session, as a couple of showers over different parts of the Spa circuit created problems, it is the championship leader who will lead away the field after ending team-mate Sebastian Vettel's run of four successive pole positions.

But on the seven-kilometre circuit in the Ardennes, pole has counted for little over the years as only 13 drivers starting at the very front of the grid have gone on to win the race from the 43 previous races.

Webber will have McLaren's Lewis Hamilton alongside him on the front row after the Briton missed out by less than a tenth of a second as a light shower at turn one late on arguably cost him pole.

Red Bull have now moved up to joint second on the all-time list as Williams (three times), McLaren (twice), Lotus and Ferrari have all had 12 poles in a season, and are now three short of equalling the record jointly held by Williams and McLaren.

Enstone-based Renault F1 team driver Robert Kubica is third, with Vettel and reigning champion Jenson Button behind him in his McLaren, followed by the Ferrari of Felipe Massa.

The Grove-built Williams cars of Rubens Barrichello - on the occasion of his 300th grand prix - and Nico Hulkenberg are seventh and ninth, sandwiching Force India's Adrian Sutil, with Fernando Alonso down in 11th in his Ferrari.

The initial 20-minute session was a chaotic affair, sparked by Vitaly Petrov who brought out a red flag after just 118 seconds.

On a damp track in places following the downpour at the end of the final practice session, Petrov ran wide over the red and white rumble strips coming out of Rivage.

That sent the Russian into a spin in his Renault, colliding with a barrier as he travelled backwards, eventually coming to a halt on the grass.

In order for his car to be rescued by the marshals, the session was halted for six minutes, crucial time lost as it turned out as the rain loomed.

Although it was only a shower over the south-eastern part of the track, it was enough to further disrupt events.

The slick tyres that all but Vettel were on at that point were not enough to cope as Virgin's Timo Glock and Jarno Trulli in his Lotus collided and were sent spinning, an incident Michael Schumacher narrowly avoided.

Although switching to intermediate tyres, Sauber's Kamui Kobayashi and Pedro de la Rosa went out in the space of a minute, the former across the gravel at Rivage, the latter at Fagnes.

Petrov will start at the back of the grid, with de la Rosa 22nd and Lucas di Grassi 23rd in his Virgin after he complained of also being caught by Trulli at one stage.

Schumacher will start 21st for although qualifying 11th, he drops down the order given the 10-place grid penalty he collected from the Hungarian Grand Prix four weeks ago for almost pushing Rubens Barrichello into a concrete wall.

Ahead of the Mercedes star are Kobayashi in 18th and the Hispania duo of Bruno Senna and Sakon Yamamoto in 19th and 20th.

On a bad day for the Brackley-based Mercedes team, Nico Rosberg also drops five places for a gearbox change after final practice, leaving the German in 17th after initially qualifying 12th.

The double Mercedes penalty means Jaime Alguersuari will start a season-high 11th in his Toro Rosso, with team-mate Sebastien Buemi 13th, sandwiching Vitantonio Liuzzi in his Force India.

With both cars in Q2 for the first time this season, the Lotus duo of Heikki Kovalainen and Trulli are 14th and 16th, their best grid slots of the year, similarly with Timo Glock in 15th.

The stewards, however, may yet intervene as they are to review the incident involving Trulli and Glock.