Hamilton heads Bottas in Mercedes one-two in opening practice

On a sweltering and sometimes breezy day in southern France, the defending four-time world champion – who trails rival Sebastian Vettel of Ferrari by a point in the title race – produced a best lap in one minute and 32.231 seconds to outpace the Finn by 0.140 seconds.

The session ended in drama with three minutes remaining when Swede Marcus Ericsson crashed heavily into the barriers at the high-speed Beausset corner, his Sauber car bursting into flames on one side. He escaped unhurt.

The Mercedes team's form reflected their determination to bounce back after a disappointing showing in Canada, two weeks ago, where Vettel’s 50th career win put him back on top.

In demand Australian Daniel Ricciardo was third for Red Bull ahead of Finn Kimi Raikkonen and his Ferrari team-mate four-time champion and current leader Vettel.

Frenchman Romain Grosjean was sixth for Haas ahead of Dutchman Max Verstappen of Red Bull, Frenchman Pierre Gasly, Mexican Segio Perez in the second Force India and Dane Kevin Magnussen in the second Haas.

The session was busy throughout, while many ticket-holders were reportedly held up in long traffic jams on blocked roads in stifling conditions en route to the track from the nearby coastal resort towns.

They missed a sequence of incidents as the teams learned their way around the "new" circuit unused for Formula One for 28 years since French hero Alain Prost won for Ferrari in 1990.

New Zealander Brendon Hartley spun his Toro Rosso to set the tone before Frenchman Esteban Ocon spun his Force India and both Saubers followed suit. In a separate incident, Hamilton had to take high-speed avoiding action when Belgian Stoffel Vandoorne was slow moving his McLaren on the racing line on the Mistral straight.

Vandoorne, who ended up 19th in a "learning" session, had also been a spinner as he searched for the limits of the track.