One of Nigel Mansell's greatest drives on his way to the world title came in Spain when he stormed from pole to the chequered flag unchallenged, despite changing conditions and a late-on torrential downpour. It was the fourth of five successive wins at the start of the season. Michael Schumacher was second, 23.9 seconds shy of becoming the youngest grand prix winner ever. The only time Mansell was rattled all day came at the post-race media conference when he was asked why he consistently played down the technical advantage enjoyed by his Williams-Renault. "Is he on the same planet or not?" Mansell snapped. "Are you serious, my friend? If you are, you should see a psychiatrist. You're stupid."
Mansell overcame mechanical glitches in his Williams-Honda to win the San Marino Grand Prix by half-a-minute from Ayrton Senna's Lotus. It wasn't a team effort either, as the other Williams driven by Nelson Piquet was sidelined after a big crash in practice. Lotus' Japanese newcomer Satoru Nakajima finished a creditable sixth despite having to switch to the reserve cars minutes before the race after a battery malfunction blew the computer on his.
Nelson Piquet won the San Marino Grand Prix to cut Carlos Reutemann's lead in the world championship to three points. Gilles Villeneuve dominated the early laps before switching to dry tyres just as drizzle started to fall. John Watson was well placed before rear-ending the "stupid" Rene Arnoux, while defending champion Alan Jones collided with team-mate Reutemann early on, philosophically saying: "I tried to go inside Carlos and he cut me off … it was fair enough."
Dutch driver Boy Hayje was born in Amsterdam. He made almost no impression in F1, only qualifying in three of the seven grands prix he entered, and then failing to finish any of those. His first entry, at the 1976 Dutch GP, was in a privately-run Penske. The story goes that he was outside the qualifying time only for associates to distract the officials and alter his official time to sneak him onto the grid.