Nico Terol became the last ever 125cc world champion in the category's farewell race at Valencia, which was won by Maverick Vinales.
Terol came into the race - the last before 125cc is replaced by the new Moto3 championship - with a 20-point lead over rival Johann Zarco, so only needed an 11th place finish to clinch the crown.
Having only qualified ninth in Saturday's changeable conditions, Aspar Aprilia rider Terol made a great start and briefly found himself dicing with Zarco's Ajo Derbi, which qualified third.
A moment for Terol then dropped him to ninth, with Zarco settling into fifth. But as Zarco tried to push for the win that was essential to his title bid, the Frenchman crashed out on the third lap.
Terol picked his way forward to join his team-mate Hector Faubel and Vinales (Blusens Aprilia) in a lead battle. Faubel had looked secure up front for the first half of the race, but fell to third as the drizzle increased around half-distance, with Vinales eventually making a break and winning by 3.2 seconds over new champion Terol.
Efren Vazquez and Jonas Folger were fourth and fifth on a disappointing day for their Ajo team.
Polesitter Danny Webb held the lead for the first lap, before being edged down to 13th as faster bikes picked off his Mahinda in today's mostly dry conditions. He eventually crashed out.
Having also used slicks to star in qualifying yesterday, Louis Rossi and Alexis Masbou slipped back to finish 10th and 22nd respectively.