 Complete the following phrase:  During the 1980s and early 1990s Prost formed a fierce sporting rivalry, mainly with Ayrton Senna but also Nelson Piquet and Nigel Mansell. In 1986, at Adelaide in the last race of the season, he beat Mansell and Piquet of Williams to the title, after Mansell retired late in the race and Piquet was pulled in for a late precautionary pit stop. Senna joined Prost at McLaren in 1988 and the two had a series of controversial clashes, including a collision at the 1989 Japanese Grand Prix that gave Prost his third Drivers Championship. 