Charles Leclerc was quickest in the opening practice session for the Singapore Grand Prix ahead of Carlos Sainz and Max Verstappen.
Leclerc's lap was just 0.078s ahead of Sainz, while the top five was separated by two tenths of a second.
Verstappen was a tenth off Leclerc's time having complained earlier in the session of downshift and balance problems, but he was still three tenths ahead of teammate and last years winner Sergio Perez who was seventh quickset.
The teams ran the Soft tyre in the last half hour of the session, with Lando Norris leading the way briefly before he was unseated by Leclerc and George Russell.
Norris later improved his lap, but it was only good enough for fourth quickest ahead of both Mercedes drivers.
Fernando Alonso was best of the Aston Martin drivers with a lap that was eighth fastest, while Yuki Tsunoda and Esteban Ocon rounded out the top ten.
Result Free practice 1 - Singapore
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Session interrupted by lizards
The session traditionally starts under twilight hours in Singapore, which means it is not representative of the actual qualifying or race.
Teams usually use it as an opportunity to test a lot of car updates, which is why you see a lot of them running flow-vis paint on the side of their cars.
McLaren was one of these with green streak of paint running across their, ironically named, 'stealth livery' special this weekend. The team has brought a raft of updates as they look to close the gap to Ferrari, Mercedes and Aston Martin.
Norris set the pace on the Medium tyres while everyone else ran Hards in the hot conditions, with track temperatures reaching 41°C in the early stages.
Before the switch to the Soft tyres happened there was a brief yellow flag for a lizard on track, which was spotted first by Verstappen.
It was the second time the Red Bull driver had an encounter with the local Singapore wildlife, after one invaded the track during FP3 in 2016.
Two further yellow flags were deployed during the session as more lizards invaded the circuit, although thankfully no reptiles were harmed.