Lewis Hamilton edged his team-mate and championship rival Nico Rosberg to lead the opening practice session at the Abu Dhabi Grand Prix.
The Briton's 1:43.476 was just over a tenth clear of the German as the Silver Arrows held a one-and-a-half second advantage over the rest of the field.
Fernando Alonso was third ahead of the man who will replace him at Ferrari next year, Sebastian Vettel, as Daniel Ricciardo and Jean-Eric Vergne completed the top six.
It was a to and fro session between the two title contenders as both swapped positions at the top of the standings throughout the 90-minute period.
With both likely keeping something in reserve, it was the size of the gap between them and rest and the field that was the most surprising.
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Williams fall apart
The usual candidates for 'best of the rest', Williams, had a horrible first session as Felipe Massa and Valtteri Bottas were left stuck in the garage as both had a failure of the bolts that connect the right-hand side bodywork to the main chassis.
In Massa's case the engine cover just came loose, but for Bottas the whole panel flew off at high-speed under braking for turn 11 and will be a major worry for the team who will hope to find a solution for the afternoon.
Another man in the wars was Jenson Button as the McLaren driver also lost out on track time with a car issue, while the exact problem was not revealed the team did confirm it was not engine related.
For the first time since Russia, Caterham were back on the circuit with Kamui Kobayashi and British rookie Will Stevens in his first full weekend.
Despite concerns over the safety of the cars and just how quick they would be everthing seemed to run relatively smoothly as Kobayashi was around five seconds slower than the Mercedes but only one-and-a-half behind the slowest midfield car.
Stevens lost out on track time as an over-revving engine needed repairing but he was at least able to get some experience from the first practice completing 14 laps in all albeit over two-and-a-half seconds slower than Kobayashi.
There were some other new faces on the track as Sauber gave Hong Kong's Adderly Fong his first official session in an F1 car and Esteban Ocon also got his first Friday session in the Lotus.
For Fong it was not the most impressive debut as he finishing 19th nearly two seconds slower than the soon-to-be axed Esteban Gutierrez in the second Sauber, but for Ocon, a man who recently beat 2015 Toro Rosso driver Max Verstappen to the Formula 3 championship, he did show some potential finishing the session only three tenths slower than Pastor Maldonado.
Second practice to be more relevant
The relevance of the first practice session could be questioned as it took place in the heat of the day, but tyres could be a factor with most struggling with the soft or prime tyres after around 20 laps, while degradation will likely be less in the cooler twilight session later in the day it will be interesting to see how the option super-soft tyres perform and whether they will be a good race tyre.
We could see a big time difference between the two compounds and we can also expect some more competitive lap times from the chasing pack in second practice which will give us a better indication of how the battle for the title between Hamilton and Rosberg could play out and whether any other teams could spoil the Briton's party.
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