Red flagpublished at 10:20 Greenwich Mean Time 27 February 2019

10:20 GMT 27 February 2019

Verstappen's incident is quickly dealt with, but not long before we stop again.

This time it's Sebastian Vettel and he has gone straight on at Turn Three and into the barriers.

Debbie's doing a grand job from the grandstand. Here's a picture of Carlos Sainz getting back out there, but it was not long before the action was halted.

Red flagpublished at 10:05 Greenwich Mean Time 27 February 2019

10:05 GMT 27 February 2019

Sainz is back out there on the track. And there is a red flag. Nothing to do with McLaren this time though.

Red Bull fans, it's your turn to be anxious as Max Verstappen stops at the end of the pit straight and his mechanics get some exercise in the hot sun as they have to push him back in to the pits.

But Sainz then promptly broke down because of a loss of water pressure.

Image source, AFP

Image source, AFP

For anyone just joining us, the big story so far today is that McLaren's Carlos Sainz has set the fastest time of any of the six testing sessions.

Image source, AFP

Andrew Benson
BBC Sport’s chief F1 writer

British-born Thai Alexander Albon was at one stage in his junior career being touted as the next big thing. His career stalled a little at one stage, but he finally has his Formula 1 chance this year with Toro Rosso.

He had never driven an F1 car before last week, and admitted at the time that its performance in high-speed corners was a bit of an eye-opener.

He said he felt much more at home on Tuesday, and now has just one day of testing left on Thursday before his first grand prix weekend.

“I’m getting more and more comfortable, especially the high speed it is getting more or less normal,” he said. “The main thing at the moment is just trying to use all the tools on the steering wheel. you can really affect the balance just by a couple of switches. It’s about getting it more natural and doing it yourself rather than your engineer suggesting it to you.”

Image source, Getty Images

McLaren have just let us know what happened to Carlos Sainz.

They say: "Carlos stopped on track because of a loss of water pressure - he should be out again soon."

Lord Roger: F1 testing in a nutshell: no one understands the tyres. McLaren does fastest time. McLaren then realises it's a McLaren and breaks down. Oh and no one understands the tyres.

Qadeer Hussain: I've been watching #F1, external since 1987 and I really should know better than to read too much into testing times, but I can't help feel a tinge of excitement that @McLarenF1, external have built a decent car this year! #ibelieve, external

Mark Meighan: McLaren stopping on track after a hot lap again. Must be spotting irregularities after pushing that they aren't when just pounding round lap after lap at a steady pace. Shows the importance of testing all aspects of the car. Best to get it all out of the way before Aus!

Sainz can stare at the timing screens that say he is top while his mechanics try to get him back out there. His car has been collected and delivered back to the pits, so we go again.

1. Carlos Sainz (McLaren, 1:17.144, 20 laps)
2. Sebastian Vettel (Ferrari, 1:18.311, 27 laps)
3. Max Verstappen (Red Bull, 1:18.395, 35 laps)
4. Valtteri Bottas (Mercedes, 1:19.205, 29 laps)
5. Daniil Kvyat (Toro Rosso, 1:19.351, 19 laps)
6. Sergio Perez (Racing Point, 1:19.704, 12 laps)
7. Kimi Raikkonen (Alfa Romeo, 1:19.758, 15 laps)
8. Romain Grosjean (Haas, 1:19.786, 16 laps)
9. Daniel Ricciardo (Renault, 1:24.122, 17 laps)
10. Robert Kubica (Williams, 1:41.622, 13 laps)

Tyres

Sainz and Kubica C4 (second softest)

Bottas, Grosjean, Ricciardo C2 (second hardest)

Everyone else C3 (medium)

Red flagpublished at 09:32 Greenwich Mean Time 27 February 2019

09:32 GMT 27 February 2019

Carlos Sainz has stopped. He comes to a halt on the main straight with the recovery vehicle off to go and get him.

McLaren fans. It must be a rollercoaster supporting your team. Some highs, some...

RonnyWelter: People are all excited about the McLaren on top while Mercedes apparently lost their ways after 5 year of dominating the sport. Yes, clearly nobody forgot that #F1testing, external times mean nothing.

Don't spoil our fun, Ronny!

McLaren fastest on Tuesday and McLaren fastest (so far) on Wednesday. I know a lot of you are going to be delighted by that.

A McLaren!

Carlos Sainz, on the C4 second softest tyres, storms through with a 1:17.144. That's more than a second clear of anyone else today, with Max Verstappen's best being a 1:18.395, although on the medium tyres.

I had to push that tweet through as it is now out of date. But who's beaten it?

Drum roll...

Before today, these were the best times of the opening five days of testing.

Jack Aitken, a 23-year-old who was born in London, came 11th in the FIA Formula 2 Championship last year and is racing for the Campos Racing team in 2019.

He is currently in Jerez de la Frontera in the opening test session for F2, where he was 17th fastest in the Tuesday morning session and 16th quickest in the afternoon session.

Today he's just tweeted his excitement at being Renault's F1 test driver.

Andrew Benson
BBC Sport’s chief F1 writer

Sergey Sirotkin is back. Sort of. He's re-emerged as Renault's third and reserve driver this year. Meanwhile, Jack Aitken is Renault's test driver.

Image source, Getty Images

Debbie's bagged herself a good spot (admittedly there are plenty to choose from). But watching testing in the Barcelona sun seems a pretty cool way to spend a Wednesday.

Hola! Anyone out in Barcelona, then we're always in the market for some pictures of what's going on.

Also, where are you keeping up to date with testing from. Anywhere glamorous or unusual? Again, any pictures and they may well go in this page. We're here all day and have a lot of time to fill!

You know the drill (hopefully). A tweet using the hashtag #bbcf1 could get you in this page.