Lewis Hamilton and a gaggle of other drivers are slowing down in an attempt to get track position and manage the tyres. Hamilton has switched over to the C6 softs but he's backed out of his flying lap fairly quickly.

Haas' Oliver Bearman is going to be investigated after the session for a red flag infringement. His team-mate Esteban Ocon, meanwhile, is not happy with a Red Bull disrupting his lap.

Nico Hulkenberg has gone fifth-quickest in the Sauber; he was fourth but he's been shifted down by the McLaren Oscar Piastri.

And now that turns to sixth, because Charles Leclerc has gone top on the softs...

Image source, Getty Images

Old foes are fighting at the top of the timesheets. Fernando Alonso is pushed down the order after his quick soft lap by the Ferrari of Lewis Hamilton, who has clocked a 1:12.025 on the medium tyre.

Image source, Getty Images

The hard tyre have been bolted on for Charles Leclerc now, just as Aston Martin driver Fernando Alonso goes quickest on a soft flyer and beats his previous marker. The Spaniard has clocked a 1:12.087.

The rookies are finding their first adventures in an F1 car at Monaco a taxing experience. Imola race winner Max Verstappen is furious on the radio as the Sauber of Gabriel Bortoleto gets in his at the swimming pool.

Over at McLaren, Oscar Piastri is getting ready to rejoin the action after his short stay in the pits hospital.

Image source, PA Media

Andrew Benson
BBC F1 correspondent in Monaco

It illustrates just how how demanding it is for the drivers in Monaco and how much they have to concentrate.

McLaren usher Oscar Piastri to safety to fix up his damaged front wing after his brush with the wall. The delay is a short one and we're back under way in Monaco.

Rosanna Tennant
5 Live F1 reporter in Monaco

A little bit of debris came off Piastri's car and flew into the Ferrari garage.

Scott Mitchell-Malm
F1 journalist, The Race

That's a harsh lesson to learn but he's got away with it - that could easily have been session over.

Piastri hits the wallpublished at 16:21 British Summer Time 23 May

16:21 BST 23 May

The second red flag of the session is out. Oscar Piastri locked up in the McLaren and went straight on into the tyre wall at the first corner. The Australian is told to bring the car back slowly.

Yellow flagpublished at 16:20 British Summer Time 23 May

16:20 BST 23 May

Charles Leclerc has just gone quickest in the Ferrari, beating Oscar Piastri's time - and now Piastri has bashed it at Sainte Devote.

As drivers file out onto the circuit, Racing Bulls get to work on Isack Hadjar's car. The French rookie is still sitting inside, so he hasn't given up hope of making it back out for second practice.

Fernando Alonso crosses the line after a medium lap and moves a couple of places into the top five. More cars complete their laps and now the Spaniard drops down once again to eighth.

Oscar Piastri goes quickest followed the Mercedes pair if Kimi Antonelli - who just set his lap on the mediums - and George Russell in third.

Image source, Reuters

Andrew Benson
BBC F1 correspondent in Monaco

There is undeniably growing tension between McLaren and Red Bull as they compete for this year's world championship. McLaren team principal Andrea Stella is possibly the most eloquent spokesperson in the entire sport. He doesn't really enjoy what Christian Horner likes to get up to, which is to really stick the needle in and twist it as hard as he can to try to wind people up. Red Bull are making many spurious complaints about McLaren's alleged technical infringements on the McLaren car, none of which have turned out to be true. Stella has had enough of it really.

The queue to get out of the pit lane is a long one, so Max Verstappen takes the time to tell his Red Bull crew about the visor tear-off that was causing him hassle at the start of the session.

The marshals, who were right next to that incident, are clearing up the track at a rapid pace so the rest of the field can get back out sharpish. Isack Hadjar's hefty hit caused quite a loud noise, bringing the session to a temporary stop after only eight minutes.

Harry Benjamin
BBC F1 Commentator in Monaco

Something I would do, playing the F1 game, but when you're in the real thing, it's not what you want to do in the early part of practice.

Hadjar makes contact with the wallpublished at 16:09 British Summer Time 23 May

16:09 BST 23 May

Isack Hadjar is now crawling slowly after his rear tyre whack with the wall at the Nouvelle chicane. The rookie is making his way back to Racing Bulls garage gingerly. Will we see him again this session?

Andrew Benson
BBC F1 correspondent in Monaco

I think it's probably wrecked the rear suspension, as well as a few other things.

Yellow flagpublished at 16:07 British Summer Time 23 May

16:07 BST 23 May

Isack Hadjar thumps into the barriers in the Racing Bulls. The rookie has come to a stop and now the red flag is out.

Times are on the board already and the quickest five runners are all on the C5 medium compound early. McLaren's Oscar Piastri was top before Max Verstappen jumps above the Australian with a 1:12.922.

Time to ring the Red Bull phone again. "Fix the upshifts," says four-time world champion Verstappen.