The Mercedes driver clocked a 1m13.425s on Pirelli's ultrasoft tyres to finish 0.196s clear of Vettel on the streets of the Principality.

It was the fastest ever lap recorded at the historic circuit.

Max Verstappen, whose Red Bull team was running a T-wing for the first time, set the fastest first sector, but lost time in the middle part of the lap and ended up third quickest, 0.346s off the pace.

The teenager spent a lot of the time in the garage, after Red Bull spotted a "potential right rear puncture" and called him into the pits, and he did his best time in the latter part of the session.

It took just a few minutes before the first serious timed lap was put on the board, with drivers keen to clock up mileage and build confidence.

Ferrari and Red Bull ran the ultrasofts straight away, while Mercedes focused its early running on the supersofts.

Vettel was the early pace-setter, but he was deposed when Mercedes swapped to the ultrasofts with just over 50 minutes to go.

Valtteri Bottas and Hamilton traded fastest laps, with the latter clocking the fastest time on the fourth lap of his run.

Bottas ended up fourth, ahead of Red Bull's Daniel Ricciardo and the Toro Rosso of Daniil Kvyat, who was the best-placed driver on the supersofts.

Kimi Raikkonen, who kissed the barrier at the Swimming Pool but escaped without damage, was seventh, more than half-a-second slower than teammate Vettel.

Sergio Perez was eighth, ahead of Carlos Sainz, who like his teammate was on the supersofts, and Esteban Ocon.

Felipe Massa was 11th for Williams, 1.192s off the pace, with Kevin Magnussen 12th.

McLaren's Jenson Button, standing in for Fernando Alonso this weekend, focused his early running on the soft tyre.

The 2009 world champion then switched to the ultrasoft to go 14th quickest, a tenth and a half slower than teammate Stoffel Vandoorne.

Romain Grosjean, who spun at Sainte Devote but continued, was 15th.

Nico Hulkenberg failed to complete a flying lap, as Renault spent most of the session investigating a problem with the energy store.

Marcus Ericsson also failed to get a time on the board after encountering a gearbox problem.