The four-time world motor racing champion Sebastian Vettel has sent an early season warning to double world champions Mercedes by clocking the fastest time on his first day of testing with Ferrari in Spain.
The German set the pace after overtaking Nico Rosberg in the pit lane on the way out for his first lap.
He was driving in a 2015 Ferrari for the first time since moving from Red Bull.
Australia's Daniel Ricciardo, who has taken over from Vettel as Red Bull's top dog, clocked the fourth fastest time.
The biggest strugglers on the opening day of the four-day session at Jerez were McLaren and driver Fernando Alonso, whose new Honda-powered car managed only six laps.
Alonso played down the poor showing, though, tweeting: "First laps. So proud of my team. Happy."
The test ends on February 4, with the season scheduled to begin on March 15 in Australia.