Championship leader Julian Simon inherited victory in the 125cc San Marino Grand Prix as race leaders Pol Espargaro and Andrea Iannone crashed together on the last lap.
Aspar Aprilia's Simon fought for the lead for most of the race with Ongetta Aprilia's Iannone, with the two opening a gap as wide as 2.6 seconds over the rest of the field.
But Espargaro, who after dropping well out of the top ten at the start had a great race with several fastest laps and plenty of overtaking moves, joined the leading pair with three laps to go in the 23-lap race and passed them.
An exciting penultimate lap, with Iannone and Espargaro switching many times position at the front, led to the final lap, where the Italian got on the inside of the Spaniard at the last corner, but went too deep, lost control, and swept out the Derbi and its rider.
After both men crashed over the gravel, Espargaro went shouting at Iannone and the latter slightly headbutted the former while the two still had their helmets on.
Simon thus went on to win and increase his lead in the championship, followed by Nicolas Terol (Jack & Jones Aprilia), who took the lead at the start, and a distant Bradley Smith on the second Aspar Aprilia.
Marc Marquez classified fourth with his KTM, ahead of Sandro Cortese's Ajo Derbi and Stefan Bradl's Kiefer Aprilia.
Fontana Aprilia's Simone Corsi was with the leading duo for the first eight laps but then dropped down the order to finish seventh.
Sergio Gadea had a lucky escape when he high-sided his Aspar Aprilia on the first lap. The Spaniard landed in the middle of the track, but thankfully all the riders that followed him managed to avoid him.
CLASSIFIED: Pos Rider Bike Time 1. Julian Simon Aprilia 40m15.301s 2. Nicolas Terol Aprilia + 0.573s 3. Bradley Smith Aprilia + 5.474s 4. Marc Marquez KTM + 9.378s 5. Sandro Cortese Derbi + 9.665s 6. Stefan Bradl Aprilia + 11.755s 7. Simone Corsi Aprilia + 23.044s 8. Joan Olive Derbi + 26.936s 9. Jonas Folger Aprilia + 32.851s 10. Daniel Webb Aprilia + 34.439s 11. Michael Ranseder Aprilia + 34.733s 12. Efren Vazquez Derbi + 35.763s 13. Riccardo Moretti Aprilia + 35.853s 14. Lorenzo Zanetti Aprilia + 39.937s 15. D.Agerter Derbi + 39.942s 16. Johann Zarco Aprilia + 40.110s 17. R.Krummenacher Aprilia + 59.051s 18. Lukas Sembera Aprilia + 59.100s 19. Luigi Morciano Aprilia +1m00.236s 20. Takaaki Nakagami Aprilia +1m01.191s 21. Luis Salom Aprilia +1m02.848s 22. Cameron Beaubier KTM +1m11.814s 23. Jasper Iwema Honda +1m11.933s 24. Luca Marconi Aprilia +1m12.053s 25. Gabriele Ferro Aprilia +1m14.596s 26. Jakub Jantulik Aprilia +1m28.731s 27. Luca Vitali Aprilia +1m29.309s 28. Jakub Kornfeil Loncin +1m29.916s 29. A.Tonucci Aprilia + 1 Lap NOT CLASSIFIED/RETIREMENTS: Rider Bike On lap Andrea Iannone Aprilia 22 Pol Espargaro Derbi 22 Tomoyoshi Koyama Loncin 16 Esteve Rabat Aprilia 15 Lorenzo Savadori Aprilia 13 Scott Redding Aprilia 5 Sergio Gadea Aprilia 0 FASTEST LAP: Espargaro, 1m43.613s on lap 20