Max Biaggi has moved to within three points of the World Superbike Championship lead after scoring a superb double on home ground, while his rivals fells by the wayside.
The Italian was duelling for the lead with Cal Crutchlow when the Yamaha rider suffered a technical problem and came down at the start of lap 13.
It left Biaggi free to complete his second double victory of the season, following on from his Portimao triumphs, but with Haslam maintaining his consistency in second, he retains his advantage in the overall standings by a slim three points.
Following an exciting four-way fight for the win in the first race, the anticipation of a repeat in race two quickly came undone when a handful of riders, including race one podium winner James Toseland, were involved in a nasty accident.
While the field had avoided contact through the Prima Variante, which has been revised for 2010 following a first corner pile-up last season, during the first race, there was no such luck on this occasion.
Tightness in the mid-field between a number of riders would prompt Toseland to get sandwiched between Jonathan Rea and Michel Fabrizio. It was contact enough for him to fall from his Yamaha, Toseland unlucky to then get caught up between his spiralling bike and the Aprilia of Leon Camier.
Sending both rider and bike somersaulting across the grass, Toseland, who has only just recovered from a wrist injury, has duly been taken to the medical centre. He will be joined there by Rea, who proceeded to come down too and spear Ruben Xaus' BMW, the pair retiring on the spot. Rea's retirement completes a disastrous day for his title hopes following his failure to finish in race one.
With the field fragmented by the accident, Biaggi emerged out front, followed by Troy Corser
– who got another excellent start to go from 12th to second – and Tom Sykes, the Briton avoiding the carnage to get his green bike into an unfamiliar position.
With Sykes being disposed of by Haslam and Crutchlow shortly afterwards, the battle for the lead was coming down to a four-way tussle between the two Britons, Biaggi and Corser.