World Championship leader Jenson Button has proved that Brawn GP are not easily going to be knocked off their perch at the top of the Formula 1 tree in 2009, by flirting with disaster before pulling a magnificent last-gasp lap out of the bag to steal pole position for the Spanish Grand Prix in Barcelona this weekend.

Down in eighth position as the clock ticked down towards the chequered flag in Q3 around the Circuit de Catalunya, the 29-year-old - already boasting a twelve-point advantage in the drivers' standings four races into the current campaign - crossed the line to begin his final flying effort with barely two seconds to spare and, fired-up, produced arguably one of the finest laps of his career in the top flight to leap to the top of the timing screens and re-instate the Brawn supremacy at the head of the F1 pecking order.

Alongside Button on the starting grid on Sunday will be Red Bull Racing star Sebastian Vettel, with the second Brawn of Rubens Barrichello - a driver who for much of the session had looked like claiming his first pole in almost five years - third and Felipe Massa taking fourth in the top Ferrari, making up in some way for the crushing disappointment the Scuderia had suffered in Q1, if not quite managing to replicate his earlier practice form when the two scarlet machines had lapped half a second clear of any of the opposition.

Vettel's challenge was spoiled somewhat when the Shanghai winner ran wide through turn twelve, with Mark Webber backing the young German up in fifth in the sister RBR, and Toyota's Bahrain Grand Prix front row pairing Timo Glock and Jarno Trulli slipping off the pace a touch in sixth and seventh, with barely anything to choose between the German-Italian combo as the Cologne-based outfit's TF109 appeared to behave better on heavier fuel than on light.

The top ten will be rounded out by fans' favourite Fernando Alonso in the sole Renault to make the Q3 shoot-out, Nico Rosberg for Williams and Robert Kubica in a BMW that has clearly improved - but seemingly not by as much as the team had anticipated.

Q2 saw Williams' Kazuki Nakajima, under-fire Renault sophomore Nelsinho Piquet, Nick Heidfeld - whose qualifying preparations were hampered by an accident in FP3 that had heavily damaged the front end of his BMW-Sauber F1.09 - defending F1 World Champion Lewis Hamilton and Scuderia Toro Rosso rookie S?bastien Buemi all fall by the wayside, with the latter skating off-piste and through the turn nine gravel trap, kissing the circuit barrier along the way but nonetheless once again out-qualifying his more experienced team-mate S?bastien Bourdais.

Up at the sharp end, meanwhile, a late flyer from Barrichello nicked the top spot, with both Red Bulls continuing to show well, Button and Rosberg narrowly saving their skin on their final efforts and Trulli and Alonso only just scraping into the top ten showdown as a mere two tenths of a second blanketed the leading five contenders.

Earlier on, all drivers had headed out in the first phase of qualifying on the softer-compound Bridgestone rubber, with nobody apparently willing to take any risks any more after seeing big names such as Massa, Kubica and Webber crash out as Q1 casualties already this season by gambling on making it through on the lesser-favoured tyres in order to save the better ones for race day. Well, nobody except Ferrari - as Barcelona in turn would claim its own high-profile victim.

Whilst Massa set the pace this time from Webber, Button, Vettel and Rosberg, all eyes were down at the bottom of the order as the seconds counted down, with Heikki Kovalainen - delayed by a hydraulics failure in Friday practice - home hero Alonso, Trulli, Barrichello, Kubica and Heidfeld all looking to be in danger of missing the cut.

With the field so closely-bunched, every hundredth was crucial and every minor error instantly magnified, and a second flying lap from STR ace Bourdais right at the close pushed Heidfeld into the drop zone. Dramatic late improvements just moments afterwards, though, saw both Piquet and Trulli haul themselves to safety - albeit the latter by the very skin of his teeth as for the first time in 2009 Toyota seem to be struggling for traction and balance - pushing former world champion Kimi Raikkonen, second-fastest in the morning practice session, out of contention.

That saw the Finn join countryman Kovalainen - back at the scene of the biggest accident of his F1 career last year, and a full seven tenths adrift of McLaren team-mate Hamilton - in the bottom five, along with Bourdais and back row Force India duo Adrian Sutil and Giancarlo Fisichella. Just as they had done with Massa in Malaysia, Ferrari made a critical error in not sending Raikkonen out again and paid a heavy price for it - meaning that on the anniversary of his last victory at the same circuit twelve long months ago, the 17-time grand prix-winner will take the start from a lowly 16th place.

To see the qualifying times in full, click here