Bastianini wins Silverstone MotoGP sprint as Bagnaia crashes
Bastianini had qualified third on the grid but took the lead from world championship contender Jorge Martin of Prima Pramac Racing on the sixth lap.
Martin had shot off the line to take the lead over polesitter Aleix Espargaro despite starting fourth and reduced the gap to Bagnaia by just one point in the championship ahead of Sunday's race.
Aprilia's Espargaro, who earlier smashed the lap record in the final moments of qualifying to clinch his second pole position of the season, was under constant pressure from Martin and managed to finish third.
Bagnaia suffered a crash at turn four, while six-time MotoGP champion Marc Marquez of Gresini Racing also crashed out.