Then triple world champion Alain Prost left McLaren to partner Mansell at Ferrari for the 1990 Formula One season. As reigning world champion, Prost assumed the role of lead driver, much to teammate Mansell's dismay. In his autobiography, Mansell claimed that Ferrari had switched his car with Prost's at the 1990 British Grand Prix without his foreknowledge. Mansell departed Ferrari at the end of the 1990 season. Prost won five races and entered the penultimate round of the season, the controversial 1990 Japanese Grand Prix, with a nine-point deficit to McLaren driver and former teammate Ayrton Senna. A controversial first-lap collision between Senna and Prost allowed Senna to secure the 1990 FIA Formula One World Drivers' Championship, with Prost ranking second.