George Russell and Lewis Hamilton led a promising 1-2 for Mercedes in Friday's first practice at Zandvoort, where local hero Max Verstappen was sidelined early on by a gearbox issue on his Red Bull RB18.
The Mercedes duo was followed Ferrari's Carlos Sainz who was 0.390s adrift, while the McLaren duo of Lando Norris and Daniel Ricciardo closed out the top five.
The second leg of Formula 1's triple-header kicked off under warm and dry conditions all round, with 22° C air temperatures while tracks temps sat at 29°C, not to mention a healthy attendance in the grandstands covered in orange.
No flares are allowed this year, but a vociferous clamour drained out the noise of the Honda V6 when Verstappen took to the track.
After a few rotations at the top of the time screen, Verstappen went quickest but ten minutes into the session the Dutchman then grounded to a halt on the exit of Turn 3, his Red Bull stranded by an apparent gearbox issue.
It wasn't a good start for the reigning world champion who is on his final gearbox element this weekend, which implies that Verstappen could be at risk of another grid penalty on his home soil.
A red flag allowed for the safe evacuation of the RB18, with the session getting back underway with 40 minutes left on the clock.
Alonso went top upon the restart with a 1m13.635s on the soft tyre, with Williams Alex Albon slotting in second.
But Norris then sprung to the top, albeit briefly as Sainz punched in with a 1m12.845s to go fastest with 30 minutes to go.
Behind the Sainz-Norris duo, Russell was third, but just 0.084s adrift, with Daniel Ricciardo and Leclerc completing the top five.
Meanwhile, Lewis Hamilton lingered down in P18, but the Briton had yet to clock a lap on the soft rubber. And when he did, the seven-time world champion leapfrogged everyone to land P2, just behind Russell who had pressed on to go top as Mercedes dialed in more pace speed.
There was little in terms of improvement in the final minutes of FP1, with positions remaining unchanged among the leaders.
Russell and Hamilton therefore delivered a promising Mercedes 1-2, with Sainz, Norris, Ricciardo and Leclerc following behind within a spread of 0.672s.
Thereafter, Sergio Perez, Alonso, Esteban Ocon and Albon rounded off the top ten.
There was little to report regarding the second half of the field, save for Mick Schumacher's productive P11, while at the other end of the spectrum, Williams' Nicholas Latifi who led the lap count closed out the running order.
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