Mercedes' Lewis Hamilton and Yamaha's Valentino Rossi swapped machines recently, the giants trading Formula 1 for MotoGP and vice versa in a much-anticipated test.
The test came together earlier this month with Yamaha title sponsor Monster Energy at the Valencia circuit.
Rossi drove the 2017 Mercedes W08 while Hamilton saddled the Yamaha YZR-11 that Rossi rode in the Valencia MotoGP season finale this year.
With Hamilton having ridden superbikes and Rossi previously testing and impressing in an F1 car before, this was much more than your usual demo run.
Get unlimited access to the world’s best motorsport journalism with Autosport Plus