Alfa Romeo Sauber driver Zhou Guanyu has ended the second day of F1 pre-season testing in Bahrain fastest while George Russell ground to a halt.

Zhou was on double duty on Friday, completing both the morning and afternoon session in the C43.

His best time came once the sun had set, the Chinese driver logging a 1:31.610s with around half an hour of track action remaining in the day.

That saw him end the day 0.04s quicker than Max Verstappen with a lap time that would have seen him seventh on the grid for last year’s Bahrain Grand Prix.

Indeed, his time was 1.6s faster than Kevin Magnussen managed on Day 2 of testing in Bahrain last year – the Haas driver having topped the session that day.

Zhou was one of those a trio of drivers who’d remained in the car for the duration of the day, the others being Fernando Alonso (Aston Martin) and Logan Sargeant (Williams).

The trio all clocked up well over 100 laps apiece, in Sergeant’s case he managed well in excess of 150 for Williams.

Conversely, Verstappen had a comparatively quiet afternoon.

After completing 157 laps on Thursday, he managed barely 50 after taking over the Red Bull RB19 from Sergio Perez on Friday afternoon.

However, the Dutchman who’d topped both sessions on the opening day in Bahrain, was still rapid and remained a permanent fixture at the top of the timesheets despite his comparatively curtailed programme.

At Mercedes, George Russell’s day came to a premature end when he rolled to a halt midway through the session.

He triggered the third red flag of testing to date – and only the second for a car stopped on track.

The Brit stopped shortly after exiting Turn 10, his car appearing to be stuck in fourth gear, before being recovered on a flatbed truck.

Russell’s team subsequently confirmed a hydraulic issue had interrupted its running, with the car not reappearing for the balance of the day.

The final 15 minutes again saw an FIA systems test, first with yellow flags, then Virtual Safety Car and finally a red flag.

Once the session resumed, the remaining time was used for practice starts and formation lap simulations.

As a result, Zhou ended the day fastest from Verstappen, with Alonso third and Nyck de Vries fourth for Scuderia AlphaTauri.

Oscar Piastri ended the day with the ninth fastest time, and 73 laps to his name, complementing the 65 of Lando Norris earlier in the day.

Sargeant has now recorded the most laps of any of the 20 drivers who have taken part in testing with 229, more than 1200km, to his name.

Verstappen is next best with just over 1100km while Valtteri Bottas has the least of the full-time drivers with just over a grand prix distance under his belt (384km).

Williams has been the busiest team with more than 1600km of running while Honda has accumulated the most data on average (when adjusted for the number of cars it supplies).

One day of pre-season running now remains beginning at 10:00 local time on Saturday, the day’s latter session expected to draw the fastest times of the test.

Results: F1 pre-season testing, Day 2 (combined)