Mercedes driver Valtteri Bottas was fastest on the final morning of Formula 1’s in-season test in Bahrain on Wednesday.

Bottas turned more laps than anyone else on Wednesday morning and set the pace with a 1.1.771 early in the session.

That time was set without Mercedes’ T-wing, and Bottas later shifted to longer stints to help try to unlock the reasons behind his own tyre struggles in the Bahrain GP on Sunday.

However, Bottas brought out the first red flag of the day just after 1pm, when his car stopped on track at Turn 4.

Force India’s Esteban Ocon set the second-fastest time of the morning, 0.371 seconds slower than Bottas, and will hand the car over to Sergio Perez this afternoon.

Daniil Kvyat was third for Toro Rosso, another 0.071s adrift, while fourth-fastest Sebastian Vettel was confined to the Ferrari garage for much of the morning.

With Ferrari having wanted to use the day for an intense data-logging programme, a change of settings revealed some problems with leaks in internal components.

That forced the team to remove the rear end of the SF70H to fix the problems, before remounting the engine and getting Vettel out again just after 1pm to add to his morning tally of eight laps.

Williams development driver Gary Paffett returned to F1 track action for the first time since 2013 to end up fifth fastest ahead of Stoffel Vandoorne, in a more encouraging day for McLaren-Honda.

After the troubles caused by an ERS water leak on Tuesday that forced an engine change, Vandoorne completed almost 50 laps in the morning without incident as McLaren was finally able to get on with a proper testing programme.