Fernando Alonso topped a wet opening practice session at the Formula 1 Japanese Grand Prix.

The Spaniard got the best of the conditions, setting his 1:42.248s on a set of intermediate tyres midway through the proceedings.

Ferrari’s Carlos Sainz and Charles Leclerc followed, ending up three-tenths away from the Alpine, before conditions worsened once more.

Kevin Magnussen was the first man out on track, breaking the sodden silence with five minutes elapsed.

He was followed by Yuki Tsunoda, the Scuderia AlphaTauri touring around on an installation lap before returning to the pits.

The track was visibly slippery, with rivers running across the road in places – particularly on approach to the Spoon Curve and out fo the opening complex.

Magnussen completed two laps before he too circled back into the lane.

Nicholas Latifi was next out, then Mick Schumacher and a handful of others, the German the first to record a timed lap at 1:50.353s.

With 20 minutes run, the circuit came alive somewhat; Leclerc going fastest with a 1:48.104s from his Ferrari team-mate Sainz.

Championship leader Max Verstappen only emerged at the halfway point in the session, opting to head out on the intermediate tyres.

Underscoring the slippery circuit was an off for Latifi, who locked up braking for the hairpin and skated straight ahead where he found the gravel but was able to drive out and carry on.

Verstappen went fastest with a 1.44.059s, slotting ahead of Esteban Ocon at 1:44.267s.

On the shallower grooved tyres, the Ferrari pair soon improved once more to top proceedings, Sainz fastest with a 1:42.563s.

That was bettered by Fernando Alonso who set a 1:42.248s before conditions worsened again.

Despite the weather, Leclerc headed out on a set of full wets, though returned to the pits with 11 minutes to run in the 60-minute session.

The two Alfa Romeo Sauber’s ventured out with four minutes to run, joined by Sainz, Schumacher, Lance Stroll, Pierre Gasly, Tsunoda, and Sebastian Vettel.

None set the world alight owing to the conditions, their presence on track had more to do with practice starts than lap time anyway.

Alonso, therefore, ended the session fastest from Sainz and Leclerc, though the times were far from representative.

After the chequered flag, Schumacher crashed, damaging both front corners of the Haas after aquaplaning at Dunlop, noting the barrier on the approach to Degner 1.

While able to climb from the car without issue, it left the team with a significant amount of work to do before Free Practice 2.

That session, which is scheduled to run for 90 minutes owing to Pirelli tyre testing, is slated to begin at 15:00 local time (17:00 AEDT/07:00 BST/02:00 ET).

Results: Formula 1 Japanese Grand Prix, Free Practice 1