In qualifying, Senna took pole ahead of Prost, Mansell, Berger, Boutsen and Piquet. However, Senna was unhappy at the side the pole was on as the pole was on the dirty side of the track and thus the second place being on the racing line which should give the second-placed driver the advantage into the first corner. He went to FISA president Jean Marie Balestre to change the side where the pole was, but was refused. After this, he decided that he would go for any gap into the first corner if Prost had the advantage. At the start, Prost did have the advantage and Senna went for the gap. Prost did not know it and closed the door. Senna's left front touched Prost's rear wing, spinning both of them into the gravel trap. The world championship was sealed.