Carlos Sainz was quickest in a heavily disrupted and red-flagged Belgian Grand Prix practice fastest for Ferrari.
In heavy rain, drivers only completed a handful of laps on a mix of Intermediate and full Wet tyres, with a 2:03.207 on the Inter enough for Sainz to top the session.
Times were largely unrepresentative in the 60-minute session, with Oscar Piastri and Lando Norris slotting in behind Sainz having also used the green-walled rubber with Charles Leclerc in fourth the leading full Wet runner.
Result Free practice 1 - Belgian
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Careful session for drivers
Alexander Albon was the first driver out at the start of the session, on the Inters, as Lewis Hamilton and George Russell both ventured out on the Wets in the Mercedes.
Albon ended fastest in this opening stage, about 1.9s quicker than Hamilton which included a moment for Yuki Tsunoda at the top Raidillon.
Sainz then returned to the track on the Inters to set his 2:03.207 lap which was enough for him to finish fastest.
A red flag was thrown about half an hour into the session when Logan Sargeant's Williams hit the barrier at the end of the Kemmel Straight into the Les Combes chicane.
He reported that "something broke" and was unable to steer.
After the session resumption, Sergio Perez and Fernando Alonso were among those to come out for exploratory laps, but no additional flying laps were set, although some drivers came out at the end of the session to complete a practice start.
Sargeant, Lance Stroll, Pierre Gasly, Esteban Ocon and World Champion Max Verstappen did not set a flying lap during the session, although did emerge for out-laps.