Romain Grosjean took full advantage of a late-race rainstorm to take a dramatic victory in the first of the weekend's two GP2 Series races at Hockenheim, seizing on a rare error from Giorgio Pantano to assume control in the closing stages.

The Italian had led away from pole, and managed to hold on to his early advantage through the mandatory pit-stops, which many teams opted to take in the opening ten laps, but the onset of rain with six laps remaining proved to be his - and others' - undoing.

Despite cars going off around them, neither Pantano or Grosjean thought about pitting for wets, confident that, not only would the shower pass quickly, but also that they had the ability to combat the increasingly tricky conditions. Both made minor mistakes as the surface caught them out, but the positions remained unchanged until three laps from home, when Pantano ran wide and allowed his rival to close the gap created by his own earlier error.

Given a sniff of victory, the reigning GP2 Asia champion wasted little time in going in for the kill, sweeping past the recovering Pantano and immediately opening out a slight cushion. Although the points leader remained fixed in his mirrors, Grosjean barely put a wheel off line over the remaining laps, and his victory was cemented when Pantano's desire to add to his victory haul got the better of him, the Racing Engineering car spinning on the final tour.

Such had been their leading pair's pace, however, Pantano's error did not prove costly, and he was able to resume still in second place, increasing his points lead over prime rival Bruno Senna despite not being able to repeat his Istanbul, Magny-Cours and Silverstone victories.

Senna had looked to be the man on a charge entering the closing stages of the race, catching and passing the category's 'form man' Lucas di Grassi for fourth and homing in on third-placed Sebastien Buemi before becoming one of the first to be caught out by the sudden change in conditions. Having run wide, the Brazilian was quickly pit-bound in search of more suitable rubber.

Although he lost time and ground by making the call for wets, Senna wasn't penalised too heavily, and immediately set about trying to reclaim as many points as possible. Getting quickly back into sixth place, he found Andi Zuber a tough customer, the pair scrapping for position before Senna found a way through with a couple of laps to run. He then made short work of Alvaro Parente when the Portuguese driver ran wide, before Zuber renewed his assault.

The pair got so close that they ran out of road on the final lap but, as usual, it was the Austrian who came off worst, failing to finish as Senna regained the road in fourth, Parente having been suitably placed to reclaim a position. Senna's loss was magnified when it transpired that Javier Villa was not going to complete the podium, the young Spaniard having disappeared from a battling third place on the final lap.

He may have been some way behind team-mate Pantano, but Villa had turned in arguably his best performance of the season until that point, qualifying strongly and racing his way into a position to assume the podium place when the conditions worsened. Instead, his loss was Parente's gain.

Behind Senna, di Grassi struggled on to claim fifth, his Campos car having become something of a sitting duck immediately before the rain arrived. First Senna, then Villa had made short work of the Brazilian, but he kept it together and was rewarded with yet another points finish on his return to the category.

Zuber's disappointment at throwing away a points finish would also have been made more bitter by the fact that Piquet Sports team-mate Pastor Maldonado came through from 15th on the grid to claim sixth place, ahead of Andy Soucek, from 16th, and Karun Chandhok, who had also been moving in the right direction before the conditions prompted a couple of spins and appeared to have dropped him out of the points.

Although he only added one to his tally, the Indian will start from the pole for Sunday's sprint race - when the conditions could be equally as tricky......