Ask any driver. Being behind the wheel for up to eight hours of a 24-hour motor race is a knackering experience.
Teams at such endurance races, including this weekend's Le Mans 24 Hours, employ at least three drivers to share the exhausting work evenly and give the others a chance to try and grab some sleep in between.
But on his way to victory at La Sarthe in 1988, Jan Lammers drove the Jaguar XJR for longer than teammates Andy Wallace and Johnny Dumfries put together.