Lewis Hamilton set the fastest time in free practice 1 for the Monaco Grand Prix after Zhou Guanyu temporarily halted the session after bringing out a red flag.
The Stake F1 driver hit the outside of Sainte-Devote, removing his front wing endplate, which was subsequently picked up by the Ferrari of Charles Leclerc.
With rain rolling in during the final 10 minutes – soon after the session was resumed – no-one would improve upon Hamilton’s leading time of 1:12.169.
It would be McLaren-Mercedes-McLaren directly behind the seven-time champion, ahead of Leclerc and the Aston Martins.
Max Verstappen and Sergio Perez would finish P11 and P12, just behind the Ferrari of Carlos Sainz, but neither ran the fastest soft Pirelli tyres.
Both RBs got themselves into the top 10, with Yuki Tsunoda leading Daniel Ricciardo in eighth and ninth, respectively.
Opening salvo
The track was immediately busy once the session began, with the field led out by the Mercedes of Hamilton.
Light rain forecast for towards the end of FP1 necessitated as much running as possible in the early stages, with all 20 drivers emerging from the pits in the opening couple of minutes.
Verstappen and Oscar Piastri bucked the trend, opting for medium tyres straight out the blocks, with the rest of the pack on the white-walled hards.
The Australian was the first driver to dip into the 1:14s, setting that time around the eight minute mark, as the lap times started to fall. That was quickly bested by Leclerc as the pack transitioned away from initial installation laps.
Nico Hulkenberg narrowly avoided planting his Haas in the barrier at Turn 1, following a lock-up and Pierre Gasly was brought back in to the pits for Alpine to investigate a suspected power unit issue in busy but uneventful first 15 minutes.
Valtteri Bottas momentarily brought out the first yellow flag of the session, after finding the Turn 1 run-off area, but a quick spin round and he was back on his way without disruption to the running.
Leclerc dropped the hammer further after 20 minutes, going over half a second clear of Lando Norris in second-place with a 1:13.343 on hard Pirellis. Meanwhile, Gasly was still consigned to the pit lane – Alpine reporting a wastegate issue on his car would likely preclude him from further participation in FP1.
Second half
As the session approached the half-way point, Verstappen set a 1:13.4, but would remain over three-tenths shy of Leclerc, with Hamilton soon splitting the two.
Piastri soon emerged on the red-walled soft tyres, with rain concerns bringing forward that section of the session. He would slot in with the sixth-fastest time, just within half a second of the leading pace.
Not long after, he would go top, inside the 1:12s. He would not head the timing sheets for long, however, with George Russell going a further three-tenths faster – also on the softs.
Although, with lap times expected to be into the 1:10s come qualifying, the pack was remained some way off the ultimate pace.
With 20 minutes left to run, the top five times were set on the red Pirellis. Piastri leading the two Mercedes, Fernando Alonso and Tsunoda.
Leclerc would soon get back in amongst the action, going third-fastest on the mediums. Thus bucking the current trend, with pack now squarely focused on one-lap qualifying simulations.
Zhou found the wall on the outside of Turn 1, giving barrier a big whack and removing his front wing endplate.
That debris would bring out a red flag shortly after, with around 13 minutes to go, after Leclerc ran over the pieces of Stake left on the racing line.
10 minutes left and the red flag was withdrawn as the rain rolled in, preventing any further movement of note.