F1 Bahrain Testing as it happened: Kimi Antonelli lays down new Mercedes marker

We are about to conduct another standing practice start. Lewis Hamilton is at the head of the field, with George Russell next. 

We are about to see another start procedure test carried out by the FIA before the end of this morning's session. This practice is to help alleviate safety concerns the teams have. 10 cars enjoyed a pretty smooth practice start simulation at the end of Wednesday's running. 

Gabriel Bortoleto puts in his quickest lap of the day so far to lift his Audi up to fifth in the timesheet. 

Pit stop practice down at Mercedes! George Russell has been in and out of the pit lane quite a lot recently to do some important work for his team. 

The latest practice pit stop was simulating a five-second time penalty, with the Mercedes crew holding Russell's car stationary in his box before continuing. 

Race simulations seem to be the order of the morning as we tick towards the conclusion of the opening session on Thursday. 

Liam Lawson is among the drivers currently lapping several seconds off the pace in his Racing Bulls. 

George Russell is also out there and has the most mileage of any driver, completing over 70 laps in his W17 on what has been a very productive morning for Mercedes. 

Valtteri Bottas and coffee - a true love story. Speaking of which, I'm off to make my second of the morning. 

"We're not here to finish P5 in the constructors' championship, we're here to be a top team. You're only really going to make those jumps if you're ambitious," Alex Albon said. 

“Yes, it's not the start of the year that we want but I'd rather us try and have these bottlenecks and these issues than be safe.

"We challenged the system, we tried to do the best job we could. We were ambitious in our targets and we just fell short to make Barcelona.

"It has exposed some areas that we clearly have realised we need to improve on. I think realistically our battle is in the midfield.

"That's our fight for now but I would say we have a huge ceiling and we're quite far away from that at the moment. I think, from our estimations, we are maybe further back from where we want to be."

Alex Albon has been the busiest driver so far this morning, completing 52 laps in his Williams. 

At the other end, Lewis Hamilton's aforementioned issues have restricted him and Ferrari to just five tours of the Bahrain International Circuit. 

Alex Albon (Williams) - 52 laps 

George Russell (Mercedes) - 50 laps 

Ollie Bearman (Haas) - 43 laps

Lando Norris (McLaren) - 42 laps 

Franco Colapinto (Alpine) - 37 laps 

Max Verstappen (Red Bull) -36 laps 

Fernando Alonso (Aston Martin) - 27 laps

Valtteri Bottas (Cadillac) - 17 laps

Gabriel Bortoleto (Audi) - 8 laps 

Liam Lawson (Racing Bulls) - 8 laps 

Lewis Hamilton (Ferrari) - 5 laps 

Only Bearman out on track now with the second hour of running drawing to a close. 

Ferrari hasn't done much running this morning, but did turn heads with its upside-down rear wing. Take a look at it below. 

Lando Norris has come back out for some running after setting the best time so far a little earlier. 

A lot of work still going on to the Cadillac. Won't be seeing that out any time soon. 

Looks like Russell is well into a race run. He's just crossed the line well over three seconds off the best pace. He's out on some C3 tyres right now. 

*Wild Valtteri Bottas klaxon*

Bottas has finally appeared on track for Cadillac, as he completes an initial installation lap an hour and 20 minutes into the morning session. 

We've not seen Lewis Hamilton for a while and the screens are back up outside the Ferrari garage. 

The seven-time world champion was sidelined with an issue for a large chunk of the afternoon on Wednesday and it appears Ferrari have run into another potential problem, having enjoyed such flawless running for the majority of pre-season testing. 

Hamilton has just five laps to his name so far and is slowest of the nine drivers to set times.