Valtteri Bottas continued his astonishing run of form in Friday practice to lead the way ahead of this weekend's Portuguese Grand Prix.
For the seventh consecutive FP1 session - Friday at the Eifel GP last time out was fogged off - the Mercedes driver was quickest, on this occasion around the Algarve International Circuit at Portimão.
It is the first time in 24 years Formula 1 has visited Portugal, and it is clear the track nicknamed 'the rollercoaster' given its undulating nature will prove to be a challenge across the weekend.
With it being a new circuit, and in particular with newly laid asphalt and heavy rain earlier in the week to make it additionally 'greener' than might otherwise have been expected, for the early laps the drivers spent their time trying to find grip which still proved to be elusive as the 90-minute session wore on.
At one stage in the early minutes, McLaren's Carlos Sainz described the situation as being like "Tokyo Drift, it's incredible" given the way his car was sliding.
A secondary issue was the stringent track limits applied by the FIA at turns one and four, with all four wheels required to be within the white lines rather than allowing a car to run over onto the kerb.
This resulted in numerous laps being deleted across the session, with virtually every driver falling foul of FIA race director Michael Masi's directive.
But come the conclusion it was Mercedes duo Bottas and Hamilton who were again out in front, with the Finn's best lap a one minute 18.410secs on the medium tyre, that appeared to grain quite easily, with Hamilton 0.339s adrift.
As has also become customary, Red Bull's Max Verstappen was the 'best of the rest', the Dutch driver overcoming an early spin emerging out of the turn four left-hander to finish almost eight-tenths of a second behind Bottas, and on the hard tyre.
Ferrari's Charles Leclerc continued his and the Scuderia's ongoing improvement in a car sporting the final batch of upgrades this weekend as the Monégasque was 0.899s down, and like Verstappen was also on the hard Pirelli compound.
Verstappen's Red Bull team-mate Alex Albon, in need of a strong weekend following poor performances in his last two races, was the only other driver to finish within a second of Bottas, 0.955s off the pace.
Sainz was sixth quickest, just over a second back, with a gap then of almost half a second to Racing Point's Sergio Perez, who was followed by Kimi Raikkonen in his Alfa Romeo, Daniel Ricciardo in his Renault, the AlphaTauri of Pierre Gasly and Ferrari's Sebastian Vettel, 1.790s down.
Lando Norris could only manage 12th quickest in his McLaren, while Lance Stroll, on his return to the cockpit after missing the Eifel GP through illness and in the wake of a recent positive Covid test, was 15th, 2.544s adrift.
At the rear were Renault's Esteban Ocon, who finished the session with smoke from the rear of his car and was ordered not to change his gear, and Williams' Nicholas Latifi, the latter 3.644s behind Bottas.
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