07:57 Good morning and welcome to day one of the final pre-season Formula 1 test of winter 2012.

07:59 No sounds from the pitlane just yet, but the session start is only moments away.

08:01 We have life, and it's Mark Webber first out in the Red Bull.

08:02 Red Bull only slightly grudgingly here today after the FIA forced it and Ferrari to reverse a plan of testing from Friday to Monday instead.

08:02 Webber is followed out by Jean-Eric Vergne's Toro Rosso.

08:03 Both are on soft tyres and pit at the end of a single installation lap. Webber is pushed back into the garage.

08:03 Sergio Perez has also done an installation run in the Sauber.

08:07 Vitaly Petrov (Caterham), Paul di Resta (Force India) and Pastor Maldonado (Williams) have all completed their installation laps too.

08:08 Felipe Massa's Ferrari and Romain Grosjean's Lotus are on track now, with Massa staying out past the pits - though this is likely to be a two-lap installation run not a flying lap.

08:08 Grosjean now back in the pits, having successfully got Lotus back on track after the drama that forced the team to abandon last week's test.

08:10 The team is hopeful that issue is now fully resolved:

Lotus optimistic chassis problems are now fixed

08:11 We started out with a track temperature of 16.7 degrees, and just that few minutes of running has brought it up to 18.

08:11 Air temperature is currently 8.1 - not too warm but a lot more cosy than last week's morning weather.

08:11 It's a sunny day in prospect with a top temperature of 16 degrees.

08:12 Nico Rosberg has done an installation run for Mercedes, and now Jenson Button is doing likewise for McLaren.

08:12 Like last week, this test features an official lunchbreak, lasting an hour from 1pm local time.

08:12 Button comes straight back in and practices arriving in his pit box at race speeds - pitlane speeds that is.

08:13 Stops perfectly on his marks, as you'd expect of the 2009 world champion. And he's wheeled back into the garage.

08:14 We've now seen all 10 cars that will be in action today, with everyone having done a single installation lap except Massa, who stayed out for two but did not do a flying lap.

08:15 We won't see Marussia here at all this week as it's new car didn't pass all the FIA crash tests in time:

Marussia forced to delay car launch

08:17 And also missing, at least for now is HRT, though it is hoping to make it out for the final day:

De la Rosa hopeful HRT can still run

08:19 Change of plan at Caterham, with Petrov in action today in place of a poorly Heikki Kovalainen, as @MyCaterhamF1 explains: "Quick Heikki update: he's down with a bit of food poisoning which he picked up overnight. Nothing too serious but a day in an F1 car is out!"

08:20 Petrov is now back on track, as is Vergne's Toro Rosso.

08:20 And it's the Russian who starts today's flying laps with a 1m33.600s.

08:22 Vergne deposes Petrov by a huge 6.3s margin as he laps in 1m27.256s.

08:22 Webber and Perez are also back out.

08:23 This is Sauber's plan for today, courtesy of @OfficialSF1Team: "Today's test programme foresees short runs in the morning and some longer ones in the afternoon. No soft tyres planned to be used today."

08:24 And Perez gets that schedule off to a flying start by knocking Vergne off the top with a 1m27.140s.

08:24 Then Vergne, on hard tyres, reclaims first place with a 1m25.959s.

08:25 Webber's first time is a 1m30.068s.

08:25 Petrov has improved to 1m30.086s.

08:25 Grosjean and Rosberg are now setting out again too.

08:26 Another improvement for Vergne at the top, as he does a 1m25.598s and increases his lead nearly 2s, just before Perez does a 1m26.930s to close back in a little.

08:26 A 1m27.6s for Perez next time around.

08:26 Improvements from both Webber and Petrov, as they do 1m27.883s and 1m29.626s respectively.

08:27 Vergne does a 1m25.639s, just off his best.

08:27 Grosjean's first lap for Lotus is a 1m34.347s.

08:28 Most are running hard tyres, with Perez the exception as he uses soft tyres on the Sauber and comes past slowly doing a constant speed run.

08:28 Rosberg clocks a 1m39.371s.

08:28 Petrov comes back in the pits. The Caterham is fourth at the moment of the six cars that have set times so far.

08:29 Grosjean pits, and Vergne comes in too, with the Toro Rosso mechanics looking poised for a practice pitstop.

08:30 Caterham just did likewise, and @MyCaterhamF1 felt it went pretty well: "That's the first pitstop of 2012 successfully completed. Good job boys!"

08:32 It wasn't a practice stop for Toro Rosso in the end, but Vergne did hit his marks perfectly.

08:32 Rosberg moved up to fifth with a 1m31.035s before pitting.

08:34 Grosjean goes fourth with a 1m29.548s. Just the Lotus and Petrov's not-a-Lotus-anymore Caterham out on track now.

08:34 Beautiful little four wheel drift from Petrov as he exits the chicane ahead of the final corner.

08:34 The Caterham now has the track to itself as Grosjean pits.

08:36 Grosjean now pits. Given Lotus's suspension issue last week, it feels like forever since Kimi Raikkonen fans got to see their man in action. And you'll have to wait a little longer too - he's not booked in until Saturday as Grosjean starts the test off.

08:36 Petrov pits, and the track is briefly empty before di Resta brings the Force India out.

08:36 And Petrov rejoins too.

08:36 The Russian has completed the most laps of anyone so far today, with 12 logged already.

08:37 Di Resta comes straight back in without setting a time.

08:37 The track temperature has now edged up to 20 degrees.

08:40 Petrov pits again, though on current form he'll probably swiftly rejoin, and Massa is now on track as well.

08:40 If you want a quick recap of everything that happened here at Barcelona last week, here's one:

Barcelona test one round-up

08:41 Massa's Ferrari has the 'periscope' measuring device attached to it yet again for more data gathering. The Brazilian is running on medium Pirellis.

08:43 Massa leaps to the top with a 1m25.413s.

08:43 Still very early days yet and that time will surely be beaten repeatedly as the morning unfolds, but the signs from last week were that Ferrari was gaining some ground after its tough start.

08:44 For the moment, the three Ferrari powered cars (Ferrari, Toro Rosso, Sauber) are in the top three spots.

08:44 Massa moves 0.7s clear of Vergne with a 1m24.828s, then laps in 1m24.9s on his next pass.

08:44 Perez, Webber and Button also out now.

08:45 We'll have to wait until Button comes past to check his tyre choice as McLaren is further down the pitlane than usual.

08:45 Perez comes back in.

08:46 Webber gets his time down to a 1m25.081s to go second, 0.253s behind Massa.

08:47 Button comes in for a practice pitstop. Still no flying laps from McLaren today.

08:48 Heikki Kovalainen confirms his absence is due to food poisoning via a more-detailed-than-we-really-wanted Tweet on @H_Kovalainen: "Wow what a night not been sick like this for a long time... both ends like no tomorrow! Not sure what I picked up and where but not nice..."

08:49 Pitstop practice remains the order of the hour for McLaren - Button dives back in, mediums off, mediums on.

08:50 And another pitstop for Button there.

08:51 Rosberg gets onto the pace for Mercedes with a 1m24.951s, putting him into second, 0.123s behind Massa.

08:53 That lap from Rosberg came on hard tyres. Massa's timesheet-topper was set on mediums.

08:57 Di Resta completes his first flying lap of the day. It's 11s off the pace, but he'll get much faster than that.

08:58 Massa comes in, does a practice pitstop, then is rolled into the Ferrari garage. Vergne does likewise.

08:58 Quietest team so far this morning is Williams: just one installation lap for Maldonado.

08:59 Busiest in the opening hour were Petrov with 18 laps (and he now pits), then Vergne on 15, Massa on 14 and Webber on 13.

09:00 Just Perez and di Resta - two men preparing to make more strides in 2012 after strong 2011 rookie seasons - out there now.

09:00 Di Resta going around 10s off even his own best, running soft tyres.

09:02 One hour down and the order looks like this: Massa 0.1s ahead of Rosberg, with Webber, Perez and Vergne next up and all within a second. Grosjean, Petrov and di Resta complete the top eight, neither Button or Maldonado have done a flyer yet.

09:02 Perez goes back to second, 0.078s off Massa, as he becomes the first man to try super-soft tyres today.

09:02 Button now leaves the McLaren garage.

09:11 Some info from Pirelli - the tyre firm has brought more medium tyres here than any other compound. 114 sets in all. Plus 69 sets of hards, 94 of softs and 38 of super-softs.

09:11 And 31 sets of intermediates and 14 of wets.

09:11 So that's a possible 360 sets of tyres that could be used here by Thursday, significantly more than were used here last week (257) and at Jerez (181) .

09:11 And that's proved that we do read the press releases Pirelli sends us.

09:12 Webber, on some medium Pirellis, comes into the pits.

09:16 Vergne goes straight to the top of the timesheets with a 1m24.379s. That's half a second up on Massa's previous best.

09:18 The Toro Rosso is running on medium tyres.

09:19 The longest run anybody has managed so far today is eight laps, which both Massa and Rosberg hae done. Rosberg's average time was 1.6s slower than the Ferraris, with both cars on hard tyres, but it's probably way too early to make any comparisons yet.

09:19 Slight correction, Vergne's new benchmark time came on hard tyres.

09:21 You can email us via live@autosport.com with any questions you have for our team of experts.

09:21 Michal from Poland has done just that to ask what tyres the cars are running. We'll try our best to spot them each time they go out, Michal. Just Vergne - on hards - out on track at present.

09:24 Vergne may be fastest now, but the evidence from last week's test was that Toro Rosso will be part of a tightly-bunched midfield. AUTOSPORT Plus subscribers can find out more in our testing blog:

Testing blog: Fast times mean nothing

09:25 Vergne is now back in so the track is completely empty.

09:30 Regular Live reader Amit Mandalia has sent this question to live@autosport.com: "With Marussia failing their final crash test and therefore not testing, and still no sign of the new HRT, do you think that this is another year of struggles for both these teams and how realistic is the possibility they we may not even see either team run in Melbourne?"

Some analysis from @eligp: "I don't think either team is under the illusion that the season will be easy for them. 2011 was already very hard for both and the fact that they are both late with their cars will make the start of the year a real challenge once more.

"Having said that, it's worth noting that both teams are undergoing a significant change to their structures that seems to be a step in the right direction to secure a more compeititive future. Will it work? Only time will tell.

"As for not running in Melbourne, it seems unlikely, but we will have to wait and see. HRT is still aiming to test on Sunday at Barcelona (http://www.autosport.com/news/report.php/id/97738), something which would be a big help for the team, while Marussia has to pass the final crash test before it can run."

09:31 Also lots of people emailing us concerned about Lotus having only completed seven laps so far following its problems last week.

09:32 So here's some timely reassurance from @Lotus_F1Team: "7 laps completed so far. We ran some sensor equipment on the car during the 1st run, takes a bit of time to remove. All part of the plan."

09:35 Maldonado sets his and Williams's first flying lap of the day with a 1m30.947s in eighth place.

09:35 Massa sets the fastest time so far in sector one in the Ferrari, going top with a 1m24.318s, 0.061s quicker than Vergne.

09:35 Petrov, Maldonado and Button are also out.

09:37 Button's pace is improving. He sets his best time of the day in 1m29.642 in the McLaren. He's eighth.

09:39 Back to the live@autosport.com question box: Oliver Heycoop asks: "Are HRT here or are they back in the factory. Surely it would be beneficial even to run the 2011 car..."

HRT isn't here today, but is hopeful of bringing its 2012 car down to the circuit on Sunday. After that, the team can still undertake a 'filming' day under the regulations. Although that would mean limiting the running to 100km (60 miles ish) and using 2009-spec tyres.

09:40 Andy emails live@autosport.com to tell us we're obsessed with food. Less so today, Andy. Kovalainen's vivid description of his food poisoning has spoiled our appetite.

09:41 Button goes fastest on a 1m24.132s, and moments later Vergne grabs second on a 1m24.216s.

09:41 Massa finds himself pushed back to third.

09:42 Button was running on soft tyres, Vergne on hards. 0.084s split the top two.

09:44 Track is pretty busy now. Vergne, Massa, Rosberg, Petrov, Maldonado and di Resta all out.

09:46 The lap that put Button on top of the times is the only real full-speed flyer he has done so far today. It was sandwiched by two much slower laps.

09:46 McLaren has done plenty of out/in/pitstop/out running, though.

09:49 So how do you keep yourself busy when your team's new car has failed its crash test? This is Timo Glock's solution, via @realTimoGlock: "Ready to jump on the bike again! Unfortunately it's not as warm as it was in Spain, bit cloudy and fresh at home."

09:49 Still sounds pretty chirpy, doesn't he?

09:50 Webber goes fastest now with a 1m23.993s.

09:50 That's the first lap in the 1m23s today.

09:50 Our tyre spotters report that the Red Bull is running on mediums.

09:53 Webber and Rosberg are the only men out now.

09:53 Massa just completed the longest run of the day with nine consecutive laps.

09:55 Six consecutive laps in that stint between 1m24.6 and 1m25.7, with a couple of 1m35 pluses thrown in. Probably backing off to give himself a gap.

09:56 And now everyone has come into the pits.

09:59 Petrov is now back out and has the track to himself.

10:00 Caterham has done some tweaks for the Russian, as @MyCaterhamF1 explains: "Front wing flap adjusted for the next run to improve balance. Car's ready and Vitaly's set for laps 27 and onwards"

10:01 Tweaks possibly carried out by one of these Caterham robots, we reckon.

10:01 The sun has been shining brightly at the Barcelona circuit this morning, the early layer of moisture well and truly gone.

10:02 And even what had been a lengthy queue in the media centre for internet cables seems to have subsided.

10:03 Grosjean's Lotus is back out, which will calm the nerves of the team's fans.

10:03 Maldonado on track too.

10:04 This is how we stand with just over two hours gone: Webber quickest on 1m23.993s, ahead of Button, Vergne and Massa - all within 0.3s. Then it's Perez, Rosberg and di Resta approximately a second off the pace, Petrov 2.9s down, and Grosjean and Maldonado yet to really get up to speed.

10:06 Grosjean and Maldonado both improve, with the Lotus doing a 1m24.996s in seventh and the Williams staying ninth with a 1m25.829s.

10:07 Perez puts on some super-softs and goes quickest on a 1m23.865s, that's beaten Webber by 0.128s.

10:11 Grosjean improves his time again with a 1m24.838s, then pits on the next lap.

10:14 Jules Bianchi (@Jules_Bianchi) tweets that he's on his way to Barcelona and popping in on his Formula Renault 3.5 team Tech 1 on the way. The Force India reserve will just be a spectator, though, as race drivers di Resta (today and Saturday) and Nico Hulkenberg (tomorrow/Sunday) have the car for the test.

10:15 Webber, Button and Vergne are the drivers on track now.

10:16 Webber has just kicked off a stint with a 1m26.0s and a 1m25.5s.

10:16 Button has just completed his out-lap.

10:16 And Vergne is onto lap six of a stint that started with a rapid 1m24.3s, then went into 1m25s and 1m26s.

10:18 Button's flying lap is very quick - he shoots back to the top with a 1m23.510s. That was on hard tyres too.

10:20 At the risk of irking everyone desperate for detailed action shots of the cars to spot the latest upgrades, we're going to illustrate Button's fast time with a portrait shot of him peeping over a wall with earplugs in and a bit of a quiff.

10:20 Button was alone on track for a while, now Massa and Rosberg are out to join him.

10:21 Webber's stint was four laps between 1m25.5s and 1m26.1s.

10:21 While Vergne pitted after five laps, his times having gone up from mid-1m24s to low 1m26s.

10:24 Well we thought Perez was on super-softs when he set the time that put him quickest for a while, but those red-ish markings were seemingly not quite super-soft red, as @OfficialSF1Team explains that he used "a set of prototype tyres from Pirelli (medium compound)."

10:25 Button goes out but comes straight back in again.

10:26 Perez sets his best time of the day on what is now a set of 'regular' mediums, lapping in 1m23.820s, 0.3s off Button.

10:30 Grosjean has now logged 15 laps in the Lotus after an hour in the pits having sensor equipment removed from the car.

10:33 Rosberg, di Resta and Vergne are the men on the track now.

10:33 Looks like hard tyres on the Toro Rosso.

10:37 Mare emailed live@autosport.com to ask: "Why there is no camera on the nose of the Caterham CT01 as all other teams?"

We asked a guy who used to hang around here on AUTOSPORT Live being obsessed with the shiny qualities of medical helicopters but now performs a crucial role for Caterham, and he said: "There are five camera positions, but teams only have to fit three and it's up to each team which three positions they want to use and which two to not use, so if there are differences between cars it's probably that one team chose to put theirs somewhere else."

10:38 Speaking of Caterham, Petrov posts his best of the day. 1m25.622 keeps him ninth, 2s off the pace, and he's done 41 laps now - more than anybody else.

10:41 On track now, Button on soft tyres, di Resta on hards, Vergne on hards, and Petrov on softs. Di Resta, running with the periscope measuring device on his Force India, heads into the pits.

10:47 News from Lotus. This morning the programme is centred around aero work that the team missed out on the chance to complete at last week's test. It will then move onto the 'more meaty' stuff this afternoon.

10:47 Lotus also says the chassis has been redesigned around its strongest part, following the issues last time.

10:48 Uday asks: "Why does pre-season testing happen on tracks such as Jerez and Barcelona and not any other tracks in Europe?"

Expert analysis from AUTOSPORT's @eligp: "Because Spanish food is the best, the people are very nice and the weather is usually great. But I may be biased..."

10:49 Webber exits the pits on medium tyres.

10:53 Maldonado comes out on mediums, and the white marked tyres help the Venezuelan to his best time of the day, a 1m25.587s, and he goes ninth, relegating Petrov to the back of the pack.

10:58 Toro Rosso sends perky vibes via @ToroRossoSpy: "All going well, Jean-Eric already ran 44 laps and it's only 11:53 am..."

10:58 And some precise news from Caterham via @MyCaterhamF1: "Just over an hour to go until lunch and Vitaly's covered 45 laps so far. Front anti-roll bar and brake blanking adjustments made for run eight."

10:59 Webber pits after a stint on mediums - four laps mostly in 1m27s.

10:59 Grosjean sets his best time of the day and climbs to fifth, 0.722s off the pace.

11:00 Quick recap of how things stand with an hour to go before lunch: Button fastest on 1m23.510s, 0.310s ahead of Perez, then Webber, Vergne, Grosjean, di Resta, Massa, Rosberg, Maldonado and Petrov.

11:01 Petrov may be slowest, but with 45 laps in the bag he has the morning's highest mileage. Vergne (44), Perez, Webber (43 each) and Rosberg (40) are not far behind.

11:02 Lowest tallies are 27 laps for Button, 26 for Massa and Grosjean.

11:02 But it's seemed a pretty smooth morning down the pitlane, with no problems reported and no red flags yet.

11:05 Essa Jumpaanen emailed live@autosport.com to ask what tyres Grosjean set his best time on. Mediums is the answer, Essa. Keep the questions coming.

11:08 Petrov goes back up to ninth with his best lap of the day. 1m25.389s knocks Maldonado down again. Petrov's tyres have no markings. Possibly more prototype Pirellis? We'll find out. Don't forget, Perez was on prototype mediums earlier on.

11:09 The press room tours have started! No love, don't take a picture of us. We're boring. There are cars out there! Far more exciting.

11:14 Vergne and Maldonado have just gone back out as Rosberg and Petrov pit.

11:15 Massa is setting off too, with hard tyres on the Ferrari.

11:15 Vivek asks: "What does the periscope on the Ferrari and Force India actually do?"

11:18 Primarily, it gives team an indication of air speed, without that air being affected by turbulence from cars ahead. It can be very useful when focusing on aerodynamic work.

11:20 A bit of stint analysis now. Rosberg has done four lots of eight laps, with his average time improving on each stint: 1m27.7s, 1m26.5s, 1m26.4s, 1m26.3s.

11:22 That compares to the 1m26.1s and 1m27.5s averages on Massa's two eight-lap runs. The Ferrari used hard and medium tyres, the Mercedes was on softs for its last two stints.

11:22 Vergne, meanwhile, has done three lots of five-lap stints on the hard tyres, average lap times of 1m25.1, 1m25.1 and 1m25.5s.

11:24 Speaking of Vergne, he's just gone on to his 54th lap. That's even more than Petrov's managed so far.

11:25 Webber starts his latest stint with a 1m24.020s lap, just a tenth off his best.

11:25 The Red Bull then backs right off to a 1m37s.

11:28 Massa is eight laps into his current stint, which has mostly been between mid-1m25s and mid-1m26s.

11:31 Rosberg sets out on softs and immediately sets his fastest time of the day so far with a 1m24.057s, putting the Mercedes fourth.

11:33 After his slow lap, Webber did another mid-1m24s, then pitted.

11:33 Grosjean jumps to third for Lotus on a 1m23.959s.

11:33 The GP2 champion is running on medium tyres.

11:35 Massa is now in the pits again. After his run of 1m25s/1m26s, the Ferrari driver slowed right down to 1m38s, and did an out/in lap.

11:37 Petrov and Vergne have now pitted to end their runs. The Frenchman did another five-lap stint on hards.

11:37 So Grosjean and Maldonado are the men now out on track.

11:38 The 1m24.0s that jumped Rosberg up the order was a one-off flying lap before the Mercedes returned to the pits.

11:39 But after his quick lap on mediums, Grosjean stayed out and did two mid-1m24s then two mid-1m25s.

11:41 Petrov holds the fastest straightline speed of the day, having been clocked at 298.3 km/h at the speedtrap on the start/finish line.

11:43 The Caterham is a full 23 km/h quicker than Button's McLaren on that chart, yet 1.9s slower on the timesheets - shows you the value of downforce at this track.

11:44 Petrov, running on super-softs, sets his best time of the day with a 1m24.876s, but it doesn't alter his ninth place.

11:48 Also out are di Resta on hard tyres, and Webber and Rosberg on softs.

11:48 Rosberg improves to a 1m23.992s and steals fourth from Webber by just 0.001s.

11:49 Petrov now pits, and by the look of the Red Bull crew, Webber is heading in as well, as Massa goes out again on hards.

11:49 After his personal best of 1m24.8s, Petrov backed off for a lap, then did a 1m25.5s, then headed in.

11:50 Rosberg comes back in, so like his 1m24.0s, that 1m23.9s came on a single flying lap.

11:52 Let's check in with Timo Glock again for another update on what F1 drivers do when their cars don't pass crash tests in time to make pre-season testing.

11:54 @realTimoGlock: "Great weather here at lake Konstanz, slight fog on top of the lake"

11:54 Di Resta pits, leaving just Massa and Perez out on track.

11:56 Rosberg is back out for what will surely be another quick outing as we have just five minutes to go until lunchtime.

11:56 Webber goes back out on medium tyres, while Rosberg pits without going for a flying lap and Massa comes in too.

11:58 Although he's not at Barcelona, AUTOSPORT news editor Glenn Freeman's (@glenn_autosport) analysis seems pretty spot on: "Reasonably close field in F1 testing today, covered by only 2 seconds. I wonder if that means teams are on pretty similar test plans today. ...or it means Red Bull is massively sandbagging and letting everyone think they have a chance!"

11:59 Perez, Webber, Massa and Petrov are all still on track with lunchtime just moments away.

11:59 Red flag.

12:00 We were expecting the chequered one...

12:00 Perez has stopped on track to prompt a well-timed stoppage at pretty much the moment lunch would've started anyway.

12:01 And here's a swift and honest explanation from @OfficialSF1Team: "No surprise as the C31 doesn't run with no fuel..."

12:01 That will have been a planned low-fuel run, not an error.

12:01 So as the red flag becomes the chequered flag, the morning ends with Button fastest ahead of Perez, Grosjean, Rosberg, Webber, Vergne, di Resta, Massa, Petrov and Maldonado - and everyone covered by just two seconds.

12:02 Petrov has completed the most laps with 67, followed by Vergne on 61 and Rosberg and Perez both on 57. And everyone has reached the mid-30s, with Grosjean's 36 and Maldonado's 37 the lowest figures.

12:03 We're off for lunch while Perez is retrieved. See you back here in an hour.

13:00 Welcome back to our live coverage of the afternoon session of the first day of testing at Barcelona

13:01 The green flags are out

13:01 But there is no activity in the pitlane so far

13:01 Just five minutes ago, we spotted Romain Grosjean down in the Lotus motorhome chatting to reserve driver Jerome D'Ambrosio

13:02 As AUTOSPORT's hard-working men on the ground filled their bellies with food

13:03 But we would like to deny we are obsessed with food, as some of you have suggested in a few emails..

13:04 Still no on-track action

13:04 And still no on-track action

13:04 We could do this all day

13:06 But thankfully we won't have to, as this morning's pace-setter Button is heading out

13:07 The Briton was fastest despite completing the fewest number of laps this morning: 27

13:07 Unfortunately the McLaren driver has returned to the pits straight away. No joy there

13:08 He hits his marks, pulls away from the pits ... and cuts the engine. Job done

13:08 But is that the sound of a Red Bull firing up what we hear?

13:09 Not anymore. It's been shut down

13:09 Our man on the ground @NobleF1 brings us some news on Lotus: Good news for Kimi fans. Lotus boss Eric Boullier says front suspension issue is now finished; updates working fine.

13:10 Back in the pitlane, nothing of notice is happening

13:11 @MercedesAMGF1: A good morning for Nico working on set-up evaluations with 56 laps completed. He's just about to head out again after the lunch break.

13:12 We can't wait

13:12 And we have noise! Button appears to have left the pits again

13:12 Rosberg, Massa and Petrov are also heading out

13:14 Some news from Force India, courtesy of @clubforce: It was a good morning for @pauldirestaf1 with 48 laps completed. This afternoon we will focus more on long runs.

13:14 And an update from @MyCaterhamF1: Lunch is done & it's straight back to work for VP. We've made changes to the front & rear ride height & the front anti-roll bar for run 12

13:15 @NobleF1: HRT's new car may not yet be in Barcelona, but its shiny new motorhome is. That badge would be a great medallion! http://t.co/o4TJouOF

13:15 Petrov, Rosberg, di Resta and Button are out on track

13:16 Petrov and Button look to be using Pirelli's hard tyres

13:17 Rosberg has posted his first time of the afternoon: a 1m28.323s

13:18 He's running softs. Di Resta is on hards

13:18 We believe Button is on hards, but it could be mystery Pirellis with no markings too...

13:18 As we said earlier, it appears there are some prototype Pirellis with strange markings about. We will confirm soon

13:19 It seems that there are no markings on Button or Petrov's tyres

13:20 We would like to remind you we have to do this the old fashioned way: that is, looking out the window to see the tyres

13:21 Button is currently the quickest man on track, lapping in the 1m26s

13:21 Webber heads out on softs, and it sounds like he did a practice starts as he left the pitlane

13:22 Petrov comes into the pits on his naked tyres

13:23 A 1m26.728s for Button on the fourth lap of his run

13:23 A Pirelli spokesperson has told us that there are unlabelled tyres out there, but they are standard compounds with no paint on them

13:24 So not mystery compounds or prototypes. Just a journalist's nightmare as there is no way to tell which is which

13:25 As we get confirmation that KV Racing will make an announcement this afternoon. Chances are it is to confirm Rubens Barrichello

13:25 Button in. Does his standard trick of stopping on the box, then shutting down the engine

13:26 Di Rest back in too, periscope and all

13:26 Told you...

@NobleF1: Our job of interpreting testing has got harder: Pirelli's latest batch of tyres haven't been coloured up yet - so no one can tell compounds!

13:27 Perez and Maldonado have jumped onto the track

13:27 Perez seems to be on supersofts, lapping in the 1:28s

13:28 Maldonado's Williams is running the medium compound

13:29 While Webber continues to run on softs, in the late 26s bracket

13:30 And now both Maldonado and Webber pit

13:30 As Webber arrives back, the mechanics are straight onto it with fans for the brakes and a cover for the rear wing

13:31 It's electric fans, not human F1 followers

13:31 Thought we'd make that clear

13:32 Perez consistent on those supersofts in terms of times. All his laps have been in the 1m28s

13:32 Vergne is back in action for STR with hards

13:33 Rosberg has gone from eight lap stints to a 10-lapper ... and counting

13:33 A very consistent drop-off in the soft tyre. From 28.3 to 30.8

13:33 He has reached 70 laps

13:35 Meanwhile, Vergne is running in the 1m27s with the hard tyres

13:36 We are pretty sure most - if not all - the fastest times during winter testing have been set in the morning sessions so far. The afternoons, with higher track temperatures, seem to favour longer runs and thus slower times

13:37 Rosberg pits as Button heads back out

13:38 And here's another photo of the new HRT motorhome

13:38 And in comes Vergne, stopping on the marks. Perez calls it quits too, leaving Button alone

13:39 Maldonado joins him

13:39 Button straight into the mid-25s. About two seconds off his best of the day.

13:40 No sign of Grosjean and the Lotus team so far this afternoon. Massa hasn't come out either

13:41 Maldonado out on softs in the Williams. He's still at the bottom of the times

13:42 Rosberg's heading back out. His last stint was the second longest of the day. Vergne has the longest at 15 laps on hards

13:43 Important issues discussed at Caterham

@MyCaterhamF1: We need you to help with a team debate from lunchtime - should tomato ketchup be kept in the fridge or the cupboard?

The answer is obvious: Cupboard until you open it. Then fridge

13:43 Oops, we talked about food again

13:43 Rosberg is out on softs, like Button

13:44 Webber joins the party on softs

13:45 Track temperature is now up to 35, double what it was first thing this morning. Welcome to spring!

13:46 Rosberg has overtaken Petrov as the busiest man today with 74 laps, but the Russian wants his lead back and heads back out

13:46 As Button pits

13:47 Petrov is on hards

13:47 Button's stint was five laps with an average of 1m25.600s

13:48 Rosberg, Webber, Petrov and Maldonado share the track at the moment

13:49 A 29.5 from Rosberg. Pretty standard at the moment, even on the soft

13:50 In fairness, no one is posting spectacular laptimes right now

13:50 As Ferrari reports that Massa will leave the pits soon to begin the afternoon programme

13:50 30.1 next time around for Rosberg. There is that degradation

13:51 That is 28s to 30s in less than five laps

13:52 Di Resta and Perez head back out, the Scot on mediums, periscope still attached to the Force India

13:53 By now, you know what we mean by periscope, we hope, but just in case..

13:53 Back to the 29s for Rosberg. He's found a bit of life in those softs

13:54 Perez is on mediums

13:54 Button, Grosjean and Massa are in the pits. The rest of the drivers are out on track

13:55 Not anymore. Maldonado pits

13:56 Rosberg and Petrov keep their personal battle going, the German on 80 laps, the Russian on 79

13:56 We are aware they aren't competing. It's all part of the show..

13:56 @OfficialSF1Team: #Sergio on lap 70 at the moment. All running well. The programme for the afternoon: runs between 8 to 10 laps. Tyre and set-up work #C31.

13:57 Lotus reports Grosjean is strapped and ready to go out for the first time this afternoon

13:57 Vergne is out on hards. Did we mention it already?

13:58 Webber's dropped off into the 31.2s. We didn't see any traffic in front of him

13:59 Grosjean and Massa decide to have a go

13:59 Everyone except Maldonado and Button on track now. It's happy hour!

13:59 Webber returns to the pits

14:00 Grosjean is using Pirelli's medium tyres

14:00 And so is Massa

14:01 The quickest man seems to be Vergne, lapping consistently in the 1m25s

14:01 Massa clocks 281km/h through the speed trap, his best of the day

14:02 Rosberg heads back into the pits after a 12-lap run averaging 1m29.942s

14:03 Eighty-five laps for the Mercedes driver. Petrov is still on track on 84

14:04 Massa joins Vergne in the 1m25s as the Frenchman returns to the pits

14:05 No one has improved on his morning time so far

14:06 Petrov pits after a lengthy run: 11 laps on the hard tyres

14:06 Grosjean pits too after a four-lap run

14:07 Petrov is now 86 laps, followed by Rosberg on 85, Perez on 78 and Vergne on 75

14:08 Massa is on the fourth lap of his run, which started in the 1m25s and is now in the 1m26s

14:08 Now the Brazilian is seen cruising slowly down the straight

14:09 It's Perez, di Resta and Massa on track right now

14:10 The Mexican Sauber driver is now lapping in the 1m30s

14:10 Di Resta and Massa have pitted, although the Brazilian kept going

14:11 Perez is also back in after a 12-lap run

14:12 Twelve laps and he lost just over two seconds on the medium tyres

14:12 Massa returns to the pits, and again heads out

14:13 A practice start for the Brazilian on the way out

14:14 Massa's Ferrari is the only car on track now

14:15 And the action comes to a stop as Massa heads back in, this time for real

14:16 Vergne breaks the silence and drives his Toro Rosso out of the pits

14:17 Looks like Massa didn't stop fully... He's back out again

14:17 Rosberg rejoins the action in the Mercedes

14:18 And guess who is back in the pitlane? Yep, Massa

14:18 Rosberg is using mediums for this run

14:19 Vergne is either on hards or unmarked. We suspect unmarked, but could they be unmarked hards...?

14:20 Rosberg hits 87 laps, overtaking Petrov with 86. But the Russian wants none of the that and leaves the pits

14:20 Massa has surprised everybody by driving down the pitlane once more

14:21 That's like the sixth time he's done it

14:22 Rosberg 88, Petrov 87

14:23 We have decided Vergne is on hards

14:24 Petrov is on unmarked tyres. Not a single bit of paint on them

14:24 But here is a bit more info from Paul Hembery on the 'mysterious' unmarked tyres: Each team has been given two 'extra' sets of them for this test. The tyres are basically Pirelli's contingency plan if its facility in Turkey should be struck by a disaster and be unable to make tyres for a race.

They have come from an unidentified facility, and the test here is simply to make sure that they perform exactly the same as the normal tyres. They are identical in compound and structure to the normal tyres.

14:24 Webber and Button hit the track

14:25 As Vergne pits

14:26 Lap watch: Rosberg is on 91, Petrov is on 89. Vergne and Perez on 81

14:26 Or you can just look at the right side of the screen, of course

14:27 Webber is on hards or unmarked. We need brighter colours for the hards..

14:28 We do know Button is on mediums though

14:29 Rosberg keeps hitting that 1m28s mark. It's the sixth consecutive time he's done it after the initial 1m27s

14:30 Button drops into the 1m26s. A long way off the pace he had this morning. But so is everybody else

14:31 @kvracing: We do have a press conference today to announce our 2012 IndyCar plans, we will tweet a link at 10am ET so you can watch live

You may want to watch that

14:31 Perez is back on track

14:32 Not many spectators in the main stand today. Surely when we hit the weekend the crowd will lift a bit

14:32 Apart from Perez's dry fuel run this morning, we've seen nothing like a red flag

14:33 Grosjean heads back out for his second run of the afternoon

14:33 He is third quickest, but has managed just 43 laps, the fewest today

14:34 It looks like hard tyre for Grosjean, but we need to confirm next time round as we've lost out tyre man momentarily. It's a two-man job to check tyres and write about them

14:35 We were wrong, it's mediums for Grosjean. That's what happens when you change the system

14:36 Rosberg just three laps away from the century

14:36 But he pits

14:37 As we say hello to the second group of tourists visiting the media centre

14:38 It was another 12-lap stint from Rosberg. he's consistent, not doubt about that. An average of 1m28.862s

14:38 Grosjean quickest on track with a late 1m24s effort

14:39 Petrov matches Rosberg's 98 laps and keeps going. The Caterham driver looks set to be the first man to reach 100 laps

14:39 Webber's times are suggesting he's on hards, marks or no marks (no pun intended)

14:40 Mid-24s from Grosjean as Petrov hits 99 laps

14:40 Our tyre spotter is back. All is good now

14:41 Grosjean pits again after four timed laps

14:41 And Petrov hits the 100-lap mark. The first man to do so today

14:41 This comes during a lengthy stint from the Russian on his unmarked tyres

14:42 Massa leaves the pits in the Ferrari

14:42 It would have been really surprising if he had lefts the pits in a different car

14:43 Vergne is on track. Looks like hards or unmarked. We need binoculars

14:44 A 1m32.437s for Petrov on his 101st lap

14:44 Definitely hards for Vergne. No binoculars needed

14:46 The track has lost a few degrees in temperature since lunch. Now down to 32.2 C

14:47 The quickest man on track is Webber in the low 1m28s

14:47 Perez and Vergne in the 1m30s. Massa has done a 1m33s

14:48 Webber passed Petrov on track and is now some four seconds quicker than the Russian

14:48 Perez heads back in as he reaches 95 laps

14:49 Nice laptime for Vergne: 1m30.333s

14:49 Petrov is in. Long stint that one as he reached 104 laps

14:50 Sixteen-lap run for the Russian. A new benchmark for the day. Average was a 1m31.706s

14:50 Massa is running on Pirelli's softs

14:51 In this 15-lap stint, Webber has dropped just one second on the hards. That would suggest Red Bull is looking very good.

14:52 And as we say that, the Australian pits

14:52 Webber's average laptime in that run was a 1m28.627s. His best a 1m27.993s

14:53 Red Bull seems to be looking on top of the grandstands to see who is spying..

14:54 Vergne, di Resta and Massa share the circuit

14:54 Remember, sharing is caring

14:55 Grosjean and Rosberg leave the pits for another run

14:55 Looks like Rosberg will be next to hit 100 laps

14:56 Di Resta stopped using medium tyres, the most common compound

14:56 Rosberg is out on the hards. Could be a longer stint for the German

14:57 Vergne still pounding around on hards. He's managed 91 laps

14:58 Grosjean into the low 1m24s. Quickest on track by far

14:58 Fifty laps for the Lotus driver

14:59 As Rosberg doubles that to reach 100

15:00 Massa is lapping in the 1m30s

15:01 A 1m25.109s for Grosjean as the session enter its final hour

15:02 Massa pits after nine laps and goes back out straight away

15:03 Grosjean is back into the pits after another short run

15:04 Vergne follows suit

15:04 Petrov goes out for another run. This time it will be 15 laps, according to his Caterham team

15:05 Vergne completed a 13-lap run, losing around two seconds at the end with the hard compound

15:05 In comparison, over 15 laps, Webber only lost a second on the same compound of tyre

15:06 Massa is running softs. Petrov is enjoying a set of unmarked tyres

15:07 Rosberg and Petrov now matched on 106 laps each

15:08 Perez also wants the 100-lap badge and leaves the pits in the Sauber

15:09 We love to see Mercedes retweeting our updates. They are following closely

15:10 Massa, di Resta and Rosberg lapping in the 1m29s

15:11 Now a discreet 1m30s for the Brazilian

15:11 On softs, remember

15:12 Perez is quickest on track with a 1m28.3 as di Resta pits

15:12 The Sauber driver is using Pirelli's hards

15:13 Meanwhile, Webber is out on track on mediums. Another 15-lap stint for the Australian?

15:14 Grosjean drives his Lotus out of the pits for another run. He's on 54 laps

15:15 In other news, Rubens Barrichello has been confirmed at KV Racing for the IndyCar season

15:15 Grosjean is on softs

15:15 Button has been quiet for a while now. He has only done 50 for the day, and very few since lunch

15:16 Straight away a lightning lap from Webber. His best of the day. A 1m23.830s that moves him up to third

15:17 Finally someone has decided to improve his time in the afternoon. Hooray!

15:17 Grosjean, on the softs, has just set his personal best in Sector 1

15:18 Webber back in the 1m32s that time, nine seconds off his last lap. Traffic, or giving his tyres a breather? Probably the latter

15:18 Vergne heads back out

15:19 Button finally heads back out for another run

15:19 Meanwhile, Petrov has reached 115 laps, with Rosberg on 114

15:21 Only Rosberg, di Resta and Maldonado are in the pits. The rest of the drivers are all having fun in the sun

15:21 Webber is back into the 1m24s

15:21 Full practice pitstop for Vergne. His first of the day

15:22 Webber dives into the pits

15:23 1m24s for Button on his 51st lap of the day

15:23 As we were saying..

@ToroRossoSpy: Pit stop practice GO GO GO!

15:24 Vergne stops again for more pitstop practice

15:25 Barrichello says he turned his attention to IndyCar two hours after he was told he would not be racing for Williams this year

15:26 Petrov completes a 12-lap run, and not 15 as promised by Caterham. His average was a 1m31.682s

15:26 The Russian is on 119 laps

15:27 Button is the quickest man on track, but lapping in the 1m26s now

15:27 Vergne is the new Massa: another practice stop

15:28 A 1m26.320s last time around for Button, who is still the fastest man on track

15:28 @Lotus_F1Team: Only a brief break for @RGrosjean as he heads straight back out on track #F1 http://t.co/Pcy5wbcT

15:29 And yet another stop for Vergne

15:30 We enter the final 30 minutes of today's session, and we predict the times will not change much (maybe that way they will)

15:31 Grosjean hast left the pits on softs. Button runs in the 1m26s. Vergne practices pitstops. And round and round it goes

15:31 We told you..

15:32 Grosjean goes quickest

15:32 A 1m23.252s for the Lotus driver on his 62nd lap of the day to move ahead of Button by 0.258 seconds

15:33 Vergne in again. And out again. We don't even need to look at the window to know it's him by now

15:33 Perez pits with 111 laps completed

15:35 Someone just did a practice pitstop. No idea who. Sounded very French, though

15:35 Maldonado comes out after a while in the pits. He has managed 53 laps

15:36 The Williams driver is out on softs

15:36 A 1m24.337s for Grosjean on the 65th lap of the day for him

15:36 Can we lobby to have Vergne's pit box moved away from underneath the media centre?

15:37 Massa heads out on hards

15:37 While Grosjean comes in after his benchmark-time setting run. That was a four-lap run for him. One 1m23s, two 1m24s, one 1m33s

15:39 Rosberg threatens Petrov's reign, completing his 118th lap of the day

15:40 Vergne's pit crew will need the day off tomorrow...

15:41 Twenty minutes left

15:41 Maldonado heads back to the pits after a four-lap run in the 1m28s and 1m29s

15:42 Toro Rosso's crew readies a set of tyres. Wonder what will happen next..

15:42 @InsideFerrari: Long runs are the main item this afternoon. Felipe has already completed 97 laps. His best time remains unchanged since this morning.

15:43 Rosberg has overtaken Petrov as the busiest man with a mammoth 120 laps

15:44 The Russian is out chasing him though. It's a close "competition"

15:44 We are considering reporting back once Vergne doesn't stop for a pitstop

15:45 Rosberg is only seven laps into this stint. Recent history suggests he'll do a few more yet. But we have been wrong before

15:46 As we enter the final 15 minutes, there are five drivers on track

15:46 And since we've been here before, we predict a red flag in the dying minutes

15:47 Massa is fastest on track, but he's only in the 1m27s

15:48 Webber heads out

15:48 Red flag

15:48 We don't like to brag, but we told you so..

15:49 Although it wasn't hard to predict, really. We know

15:49 It's not Rosberg, or Massa or Webber

15:49 Petrov is the culprit. He has stopped at Turn 6

15:50 It's very likely to be a dry fuel run but we will confirmed as soon as we know

15:51 The Caterham is now being covered up

15:52 While they recover the car, you can go read some news:

Pirelli could make softs more aggressive

15:52 And here's the story confirming Barrichello:

Barrichello commits to full season

15:53 The green flag is back out

15:53 No oil reported at the scene of Petrov's stoppage

15:54 A couple of engines start up with six minutes left

15:54 Grosjean, Perez and Vergne head out

15:54 Webber does too from right underneath us. Medium tyres for the Australian

15:55 Rosberg joins the action too

15:55 The quickest five drivers of the day are out on track at the moment

15:55 A car stopped at the pit exit. Sunlight is low so we can't tell who it is

15:56 It was a practice start

15:56 Massa is out on mediums

15:56 Only Petrov and Maldonado are not on track

15:57 Another practice start for somebody. Goes very slowly onto the track. Meanwhile, big lock-up from Grosjean going into turn 1 as he sails past the slower car

15:58 Vergne comes down pitlane very slowly... and it's happened! He hasn't made a practice stop!

15:58 Just 90 seconds remain now, with eight drivers on track

16:00 Nobody looking likely to improve...

16:00 The chequered flag is out

16:00 Vergne pits without completing that last lap. Massa stays out and crosses the line though

16:01 Any long runs were pretty badly affected by the Caterham-induced red flag

16:01 Di Resta pits. Rosberg pits

16:02 And everybody else except Massa too. The Brazilian will be the last man to return to the pits

16:02 But it will not change the order, with Roman Grosjean finishing on top of the times on the opening day of the final day of testing at Barcelona

16:03 Just the two improvements this afternoon, although they were pretty significant with Grosjean going top and Webber P3

16:03 Rosberg has been the busiest man with 128 laps completed, more or less the same amount of pitstops done by Vergne

16:04 We will be back from 9am CET tomorrow for the second day of testing. Thanks for reading us!