Isack Hadjar is making his way through Turns Five and Six but one of the Williams is blocking his path to a smooth exit. The Racing Bulls vents his frustrations over the team radio, letting his pit wall know he's far from impressed by other driver's track etiquette.

Gabriel Bortoleto only reaches Turn Two in the Sauber before his cold soft tyres give up and stop the Brazilian going any further. The final 18 minutes of this session could be quite frantic.

Oscar Piastri has rejoined the field after his earlier issue but he's now playing catch-up to his team-mate Lando Norris, who is sitting top of the timesheets with a 1:43.747. Piastri's first timed lap lifts him to ninth on the board.

Andrew Benson
BBC F1 correspondent

I can't be 100% sure but I've been told by a team that it was a red flag even though the timing screen was not showing as red. As far as the teams are aware, the session was red-flagged.

That was all very odd. But we're back under way, with the piece of kerb rubber hopefully stuck down nice and tight.

Oscar Piastri is ready to go - have the mechanics fixed the problem with the Australian's car? Not that he can actually go anywhere, as the track is still under a yellow flag.

Rebecca Clancy
F1 journalist on BBC Radio 5 Sports Extra

I-Cat Hadjar! He was there all day yesterday. I think it's a Bengal cat, it's absolutely beautiful.

I am not claiming I-Cat Hadjar as my own, I heard it yesterday and stole it. Send in your cat F1 names - #bbcf1

Image source, Getty Images

Yellow flagpublished at 10:02 BST

10:02 BST

There are still no cars on track and the signals keep changing in Baku. The pit lane is closed, but messages have flashed green to say the circuit is clear. The red flag has now switched to yellow and everyone is still waiting.

Seems to be the kerb at Turn 16 is causing the issue, with some rubber coming loose when Carlos Sainz took the corner before the stoppage.

Andrew Benson
BBC F1 correspondent

Before the red flag, Oscar Piastri was in the pits and the engine cover was off so it looks like that car has come kind of problem. Not what Piastri needs in this first session.

Andrew Benson
BBC F1 correspondent

Charles Leclerc is just absolutely brilliant around here. He is good at street circuits generally, he's got a similarly fantastic record at Monaco and one of his greatest laps ever was at Singapore in 2019, It's something about his ability to dance the car on the edge of adhesion with an sharp front end without losing control. It really plays to strengths.

Image source, Reuters

The marshals have cleared the debris from the track now but it doesn't look like we'll see Oscar Piastri heading out on track right away.

We also heard a radio message from George Russell during the delay. "Serious bottoming out on the straights," he says, while sounding absolutely dreadful.

Image source, Getty Images

The weather forecast could be a mixture of sunshine and light rain across the three days of track action, with gusty winds also predicted during qualifying.

Friday's practice sessions are the most settled, with clear skies and temperatures of about 25 degrees, while Saturday's third practice and the fight for pole position, plus Sunday's grand prix, could see rain in the morning before dry conditions take over.

Red flagpublished at 09:46 BST

09:46 BST

George Russell briefly beat Lando Norris' quickest time with a marker of 1:44.150 but the McLaren driver jumped back to the top of the timesheets before the red flag was shown with a time four-tenths faster than the Mercedes man.

Red flagpublished at 09:44 BST

09:44 BST

Everyone back to the pits - and Pierre Gasly can tell us why.

"There's a piece of carbon at the last corner," says the Alpine driver.

While Oscar Piastri can only stand in the garage and watch the monitors, his team-mate Lando Norris has gone to the top of the timesheets on the soft C6 compound with a 1:44.274.

Image source, Getty Images

Oscar Piastri has climbed out of the car over at McLaren. The Australian takes off his race helmet and is now watching the mechanics quickly trying to assess what the issue might be. This isn't the best start to the weekend for the man who is leading the championship by 31 points.

There's another message incoming from McLaren, this time heading Oscar Piastri's way. The title leader is given a list of instructions before making his way back to the pits for a check-up.

Meanwhile, George Russell is calling in to Mercedes. "I can smell a bit of burning, I think it's the brakes," says the Briton.

Image source, FIA

The list isn't long for Azerbaijan updates but the chasing trio of Ferrari, Mercedes and Red Bull have all brought minor tweaks to Baku.

Racing Bulls

Front corner, rear corner.

Ferrari

Front corner.

Mercedes

Front wing.

Red Bull

Rear corner.

Lando Norris, second in the championship to his team-mate Oscar Piastri, is told to box by McLaren. It looks like the team have spotted a rogue item that's been left on the car.

Over at Sauber, Gabriel Bortoleto bails out to one of the escape roads on his opening lap as he tries to get to grips with the tricky Azerbaijan street track.

Andrew Benson
BBC F1 correspondent

One of the big questions for the weekend is whether that win for Max Verstappen in Monza two weeks ago was a one-off or whether it was reflective of them finding something in the car.

Obviously that's not George in the previous entry. That's a cat that was the talk of the paddock yesterday.

The soft tyres are bolted on first and we've got the likes of Franco Colapinto, Nico Hulkenberg and Liam Lawson out on the Baku streets early.

Image source, Getty Images