Changing conditions at the Nurburgring caught out many drivers during a wet, time-limited sprint race on a cold and grey Sunday morning.

The track was emphatically wet from a pre-race downpour and ongoing slight drizzle, but not to the degree seen at Silverstone where a start behind the safety car was required, so the cars and drivers had to go for wet tyres and set-up and then struggled to find the acceptable limits of grip as the lights went out for the start of the sprint race.

Polesitter Sam Bird struggled to get away and keep the lead from a flying Giedo van der Garde who stormed down the middle between Bird and Dani Clos, the Barwa Addax car briefly taking the lead through turn 1 before Bird was able to take back control. That left van der Garde tangling with Racing Engineering's Clos, and the two came together in the entry to turn 5 and flew off the track, ending both drivers' races.

If Bird thought that was the end of his problems, he was sadly mistaken as he misjudged turn 10 two laps later, put a wheel onto the wet kerbing and spun off onto the grass, dropping several positions before rejoining in seventh place.

That left Jules Bianchi in the lead of the race ahead of Romain Grosjean, ahead a third Frenchman Charles Pic who was struggling to stay ahead of feature race winner Luca Filippi. Their battle allowed the lead duo to break away, with Grosjean looking fast initially but Bianchi clearly able to stay in control of the race and by lap 7 had been able to eke out a 4s lead over his compatriot.

His Lotus ART team mate Esteban Gutierrez confirmed how the team had really nailed a wet weather set-up and was surging: on lap 6 he took fourth place from Filippi at turn 1 only for the Italian to fight back and reclaim the position a few corner later in an epic developing battle; next time through turn 1, however, and with Pic struggling under braking Gutierrez not only had a perfect opportunity to overtake Pic, he was also able to pass Filippi in the same move with a bit of wheel-banging and vault up two spots to third place. While Pic and Filippi's ongoing battle allowed Max Chilton the chance to overtake them both later in the lap, Gutierrez was clearly the fastest man on the track and was quickly out of reach, soon scything through the gap between himself and Grosjean.

By contrast, yesterday's race winner Filippi was looking distinctly unhappy with the state of affairs and on lap 10 he was passed by AirAsia's Davide Valsecchi for fifth in turn 1. His Coloni simply didn't seem to be handling well in the marginal conditions, and with all the cars increasingly having to seek out standing water down the straights to cool their wet tyres it seemed like it was time for an audacious switch to slicks on lap 11.

And a risk it certainly was - Stefano Coletti had made an attempt to go to slicks on lap 7 only to quickly spin out of the race, and conditions were still bad enough on lap 10 to cause the experienced Alvaro Parente to spin the Carlin car out at turn 3. But Filippi wasn't alone in his gambit, and at the end of lap 11 he was joined by other front runners including Pic and Bird in a dive for pit lane and a new set of dry weather tyres.

Pretty quickly it was clear that the slick-shod cars weren't simply flying off the track anymore, and their time was several seconds faster per lap, so next time around a whole lot more cars led by Adam Carroll picked up the strategy and arrived on pit lane.

At the front, Gutierriez managed to get second place from Grosjean through turn 1 only for Grosjean to fight back and take the position back; at the end of that lap, however, they both came in to pit lane together and the Lotus ART pit crew out-performed their Dams rivals and put Gutierriez out first, forcing Grosjean to hold momentarily to avoid an unsafe release into the side of the young Mexican driver's car.

Jules Bianchi had opted to stay out to this point, deciding that track position was worth the delay; but the writing was on the wall compared with the times of those on slicks - especially Luca Filippi who was now the fastest man on track - and he came in on lap 13, handing the lead to Davide Valsecchi who like his AirAsia team mate Luiz Razia and Dams' Pal Varhaug was yet to stop.

Valsecchi had a 15s lead when Bianchi came in; two laps later and that lead was gone, Bianchi was all over the back of him and finally the two AirAsia cars gave up all hope that conditions might worsen and headed for pit road, allowing Bianchi to reclaim the lead once more. Only Varhaug would stick doggedly to the wet tyres to the bitter end, and his reward was to go a lap down by the chequered flag; Razia's delay in pitting meant he would finish in 14th, while Valsecchi ended up colliding with Jolyon Palmer on his exit from pit lane which put both cars out on lap 18; Valsecchi was judged to have been guilty of causing the collision and was subsequently handed a ten grid position penalty for next weekend's Budapest feature race.

While things were looking good again for one Lotus ART driver, suddenly they were looking rather less so for his team mate. Esteban Gutierrez was struggling and lost positions to both Grosjean and Filippi; finally the reason was clear, as Gutierrez found himself overtaken by his rear right wheel into turn 11 as he detached itself and made a break for freedom. Gutierrez was able to control the slither down the hill on the wet grass, but had to retire from what had looked a promising race for him.

With the race now time-limited and the clock ticking down to under ten minutes to go, the top three - Bianchi, Grosjean and Filippi - were locked together with little more than a second covering all of them for lap after lap. Bianchi seemed to be slightly holding them up, with fourth-placed man Christian Vietoris now putting in the fastest laps of anyone, but he was 18s back and didn't have the time to become a real factor in the race outcome despite his speed

Sure enough, Grosjean was able to make a move on Bianchi into turn 1; but Bianchi fought back and Grosjean stumbled over Filippi who was trying his own move on them both and the status quo was restored, but it was clear that the race win was wide open and there for anyone to win - or to lose.

The crucial moment came as the trio ran down to the final chicane for what would be the penultimate time: Bianchi's poor handling showed and he slid through the chicane, giving the momentum to Grosjean who got the better drive down into the final corner onto the start/finish straight. Grosjean made no mistake and nailed it, but Bianchi was still close enough to mount a fightback going into the prime overtaking opportunity of turn 1.

Fortunately for Grosjean, Filippi had designs on second and tried a frankly optimistic move down the inside of the corner. Bianchi wasn't expecting it and sliced across him with minor contact, not enough to do any serious damage but enough to cause both cars to falter for a vital second or so. If there had been longer than a lap to go then they would have been able to bounce back, but as it turned out there wasn't time before Grosjean took the chequered flags at the end of lap 23.

Grosjean's victory capped a strong weekend for the GP2 series championship leader, which was made even better when one of his closest rivals Charles Pic was black flagged and excluded from the race results for failing to serve a drive-thru penalty in time, incurred when he cut the pit lane blend line when he came out of the pits on slick tyres. Rodolfo Gonzalez also received a drive-thru after he made contact with Johnny Cecotto on lap 7 which put the Ocean Racing technology car out of the race.

As a result of Pic's misdemeanour and van der Garde's early exit from the race, Grosjean now leads the championship by 18pts with only three weekends to go. His domination is by no means water-tight or of Vettel-esque proportions, but 2011 is starting to look very good indeed for the former Renault F1 driver, who will be hoping to maintain the momentum going into next weekend's round in Hungary.