ABU DHABI (Reuters) - Red Bull's Max Verstappen was fastest in first practice for the season-ending Abu Dhabi Grand Prix on Friday but five times Formula One world champion Lewis Hamilton made sure everyone knew who was number one.
With both titles already won by Mercedes for the fifth year in a row, Sunday's race should be a no-holds barred battle for victory without team orders or other considerations.
Verstappen, at the centre of attention in Brazil two weeks ago after a collision with Force India back-marker Esteban Ocon led to a post-race confrontation, laid down a lap of one minute 38.491 seconds.
Australian Daniel Ricciardo, in his last race with Red Bull before leaving for Renault, was second fastest and 0.454 slower than his on-form team mate.
Valtteri Bottas, last year's winner in Abu Dhabi for Mercedes but still chasing his first victory of the season, was best of the rest with Hamilton fourth but both using harder tyres than Red Bull's hypersofts.
Hamilton does not use the number one reserved for the champion, preferring his favourite 44, but on Friday the Briton lapped the Yas Marina track with the single digit prominent on the front of his car.
"Lewis has requested and been given permission to run the number one on the nose at this final race of the season because he's world champion," explained a team spokesman.
"And it's even a nice shade of metallic red to match his helmet."
Hamilton wrapped up the drivers' title in Mexico with two races to spare while Mercedes secured the constructors' crown in Brazil for their fifth successive championship double.
The Briton was gifted victory in Brazil by Verstappen's collision but he still had to nurse an ailing car to the finish with Mercedes worried his engine was about to fail and turning down the power.
Mercedes said they were using the same engine for practice, after finding a failure in the variable inlet system that caused unstable combustion, with some permitted hardware changes and would review the data at the end of the day.
Ocon was fifth fastest, in what looks likely to be his last race for a while with Canadian Lance Stroll set to take his place, and Kevin Magnussen sixth in a Haas.
Ferrari's Kimi Raikkonen, preparing for his last race with the team before joining Sauber, and season's runner-up Sebastian Vettel were seventh and eighth.
Poland's Robert Kubica, announced on Thursday as a 2019 Williams driver, was also on track testing car developments and without chasing a quick time.
He was last on the timesheets, more than four seconds slower than Verstappen.
Sauber's Marcus Ericsson, also moving on after Sunday's race, spun at turn one and hit the barriers.
(Writing by Alan Baldwin in London, editing by Patrick Johnston)