Lewis Hamilton edged out Mercedes team-mate Valtteri Bottas in first practice for the French Grand Prix.
Hamilton, who heads Bottas in the championship by 29 points, finished seven-hundredths of a second clear of the Finn at the Circuit Paul Ricard.
Ferrari's Charles Leclerc was third ahead of Red Bull driver Max Verstappen, with Sebastian Vettel fifth.
Hamilton's Mercedes team head into the race in southern France unbeaten from the opening seven rounds, and the Silver Arrows had the edge over the rest of the field in the first running on Friday.
Hamilton, who was excused from his media duties on Thursday to attend a memorial service for the renowned fashion designer Karl Lagerfeld in Paris, held the advantage over Bottas by just 0.069 seconds.
Bottas turned the tables on Hamilton later in the day, beating his Mercedes team-mate to top spot.
Bottas finished nearly half-a-second clear of the Briton, with the Ferrari pair of Leclerc and Vettel third and fourth respectively.
Hamilton, however, is facing a stewards' investigation after he ran off track at the fourth bend before rejoining in front of Verstappen. The Dutchman fell off the circuit avoiding the recovering Mercedes car.
Ferrari, meanwhile, await the verdict of their hearing with the FIA over Vettel's five-second penalty in Canada.
Ferrari sporting director Laurent Mekies presented his case to the stewards in a meeting which lasted 35 minutes.
Speaking ahead of the hearing, Mekies said: "We have requested the FIA's right of review because we believe that this evidence is quite overwhelming when it comes to establishing that Sebastian did not breach any regulations."