1625: For those of you who arrived late and are keen to find out what happened today, I'd heartily recommend your read all 5,800-odd words of this text commentary. Failing that, why not take a look at Sarah Holt's report from the Circuit de Catalunya. We're back again on Saturday at around 0800 so be sure to join us. Thanks for all your contributions. It's been a pleasure.

1615: It's been a tremendously busy day both on and off the track, so I'd urge you to stay across bbc.co.uk/f1 for any developing stories - particularly the one concerning Bahrain.

1610: So here's the final rundown from day one of four in Barcelona. Vettel (one minutes, 24.374 seconds), Alonso (1:25.485), Alguersuari (1:25.638), Kobayashi (1:25.641), Button (1:26.365), Di Resta (1:26.575), Barrichello (1:26.912), Schumacher (1:27.512), Karthikeyan (1:28.393), Kovalainen (1:30.065), D'Ambrosio (1:30.950), Petrov (1:35.174) and Heidfeld (1:44.324).

1600: Out comes the chequered flag and the Herr from Heppenheim has only gone and done it. At 1530 I urged someone to steal the show and, typically, it was the reigning world champion who stepped up to the plate. The Circuit de Catalunya crowd spent much of the day marvelling at their hero Fernando Alonso's fastest time, only for the pace-setting mantle to snatched from his grasp at the last.

1555: ALERT: World champion Sebastian Vettel registers a lap of one minute, 24.374 seconds to go top of the timesheets. "Is he that confident" asked F1 Fanatic when the German had only put in 23 laps. "Yes he is" would seem to be the answer. Vettel's time is 1.111 seconds quicker than the Alonso mark which stood since before lunch.

Renault GP on Twitter: "Vitaly is back on track finally getting on with our pit stop practice."

BBC pit-lane reporter Ted Kravitz: "Arriving halfway through the first day in Barcelona it's clear the whole of the Formula 1 paddock's mind is on Bahrain. Team representatives are gathering here for a meeting later this evening and the general secretary of teams' organisation Fota is also here. Following Bernie Ecclestone's initial pessimism, the mood is increasingly that not only will the test, which begins on 3 March, not go ahead but the race is looking like becoming impossible to stage, for obvious reasons. The teams need to make a decision as far as the test goes by Monday lunchtime because that will affect whether they send their race trucks back to the factories or to another testing venue in Europe."

1545: A run of 15 flying laps for Schumacher but he's down to eighth with a quickest time of 1:27.512. The biggest mover in the top 10 is Di Resta, up to fifth with a 1:26.575. Saltires at the ready.

1540: Alonso immediately returns to the track as Vettel clocks a 1:26.584 - his quickest lap of the day. Barcelona's Circuit de Catalunya is now completely dry so it's reasonable to expect a challenge to Alonso's pre-lunch 1:25.485. Unless, that it, the big guns focus on longer stints in the last 20 minutes.

1535: Here we go... Vettel emerges from the Red Bull garage, Button's out too, and Schumacher makes it a hat-trick of past world champions. Alonso heads into the pits after a 17-lap run but plenty of big names still out there.

1530: Half an hour for someone to steal the show. Come on, chaps, give us something to natter about. Could get tasty.

1527: A lot of you saying there's no way final testing and the season-opening Grand Prix should take place in Bahrain amid the current unrest. Here's what Williams team chairman Adam Parr had to say on the issue: "We would be very disappointed if we were unable to start our season in Bahrain. We want to make a positive contribution to the countries that we visit and our intention is always to be there as a positive presence. If that were not to be the case, we would not want to make a negative impact. Clearly if Formula 1 were to become a focal point of unrest, that would be a concern," he added. "It's not just about the safety of those involved but being sensitive to what is going on in the country."

Anon via text on 81111: "Mclaren are not showing up at all, are they hiding their pace or they don't have it?"

F1 Fanatic on Twitter: "Vettel has done 23 laps in his Red Bull, much less than his rivals. Is he that confident?"

1515: Forty five minutes remaining and Alonso (one minutes, 25.485 seconds) still leads, but Kobayashi (1:25.641) is up to second and so Alguersuari (1:26.117) gets pushed down to third. Button (1:26.365) finds himself fourth with Vettel (1:36.640) fifth and yet to register a timed lap this afternoon. Barrichello (1:27.447) is sixth, Schumacher (1:27.512) seventh and Di Resta (1:28.348) eighth. Then come Karthikeyan (1:28.393), Kovalainen (1:30.065), D'Ambrosio (1:32.068), , Kobayashi (1:30.950) and Heidfeld (1:44.324).

Renault GP on Twitter: "A few issues with the KERS software today. Hopefully Vitaly will get some running before the end of the session."

1500: Cometh the hour, cometh the man. Alonso hits the Circuit de Catalunya on fresh tyres, so let's see what the Spaniard can do in front of his adoring fans. Out comes Di Resta, too, and he's up to eighth with a 1:28.348.

1458: Force India bring their Brit into the garage. Intrigued to see how many laps Paul gets under his belt in Di Resta today. Oh dear. Meanwhile, Schumacher and Karthikeyan are jostling for fifth and sixth and Button is back out on the track. Kobayashi marginally improves his best time (1:26.666) but remains fifth, behind pace-setter Alonso, Alguersuari, Button and reigning world champion Vettel.

A snap of Nick in his BMW Sauber days

BBC Sport's Sarah Holt in Barcelona: "Diminutive Nick Heidfeld was almost swamped by media as he made his first appearance since being announced as the injured Robert Kubica's replacement at Renault. After wishing a speedy recovery to Kubica, Heidfeld was asked for his opinion on whether Formula 1 should go to Bahrain in light of the recent unrest. Heidfeld said it was too difficult for him to judge before adding: 'Nobody likes the idea of going somewhere where you could be potentially endangered.' The experienced German also refused to be drawn on whether Renault, who have twice topped the testing timesheets, could have closed the gap on their rivals saying: 'Everyone is really in the dark but we have strong ambitions. Wait and see.'"

1445: Di Resta fans, your man has finally joined the party. The Scot posts his first timed lap of the day - a 1:31.665 effort - to put himself 10th on the timesheets.

BBC Sport's Andrew Benson: "This is one of the most intriguing questions of the Barcelona test. It's fair to say McLaren had a troubled first test with their new car in Jerez last week, not getting in a lot of running after what they said was a shortage of spare parts. Barcelona is therefore the first chance to get some idea of its pace - and we hope to provide some analysis of that here on the BBC over the next few days. All we can say for now is that McLaren's first test contrasted noticeably with those of Ferrari and Red Bull, whose cars have run pretty much like clockwork so far - and looked very fast as well."

1441: Mr G, you still there? If so, I've an answer for you from Mr B...

1440: Button chalks off four timed laps before returning to the garage. The best he can manage is a 1:28.073, nowhere near his top morning-session time of 1:26.365. Britain's 2009 champion does, however, remain third behind Alguersuari and that man Alonso.

Marc, from Cardiff but in Barcelona, via text on 81111: "Just arrived at the Circuit, the noise is something else."

1430: Kobayashi up to fifth with a 1:27.340. And out comes Button for his first post-run lunch. Alonso still heads the field after his pre-lunch 1:25.485 but his hopes of improving on that have, for now, been scuppered by the two red flags we've seen this afternoon. The Spaniard has started to focus on long runs but as his Pirellis started to go off, his time began to drop and Ferrari called him into the pits.

Renault GP on Twitter: "An update on Robert: He is due to be transferred from intensive care to the rehabilitation department to continue his recovery…"

1422: Meanwhile, a new addition to cars this season is the adjustable rear wing. Again, it's activated at the push of a button, changing the angle of the rear wing to get less drag and improve straight-line speed. It can be used at any time in practice and qualifying but, in the race, only less than a second behind the car in front at designated points on the track. It's designed to promote overtaking but could prove a little mind-boggling.

1420: Quite a few questions about our dear old friends the kinetic energy recovery systems (Kers). To clarify, they're back for the 2011 season after a one-year absence and drivers will use them to boost overtaking. The systems take waste energy from the brakes and turn it into a power boost at the push of a button.

1410: Just Alguersuari and Karthikeyan on the circuit at present, the latter going round in 1:28.393 to move up a place into eighth.

Simon, Northampton, via text on 81111: "Can you tell us what times the recovery truck is setting…? It must have plenty of laps completed by now."

1406: Alguersuari's machine returns to the Toro Rosso garage and we're back under way, D'Ambrosio first to hit the in his Virgin MVR-02.

BBC Sport's Sarah Holt in Barcelona: "Hello again. Just a little snippet of news for those of you asking about Paul di Resta's absence on Friday's timesheets. The word from the team is that the Force India car "isn't ready yet". You may remember that Di Resta went off in the closing stages of Sunday's Jerez test and broke his left-rear suspension in the process."

Good morning, Barcelona

1359: Depending on how you're following this text comm, you should be able to see the pic I've posted with this entry. It shows one of the 12 cars lapping the Circuit de Catalunya this morning as the sun rises behind some nearby mountains and mist lingers in the foreground. One of the joys of winter testing. Simply stunning.

1355: I regret to report that we have another RED FLAG, our third of the day. Alguersuari into the gravel at Turn 4, recovery truck comes out to play once more.

Mr G, London, via text on 81111: "After McLarens high profile launch of their new innovative car there's not been much reported on their out right pace. Are they keeping it under wraps or is their pace not up with Red Bull and the Fezzas yet?"
Fair question, I'll ask our F1 expert Andrew Benson to get back to you with an answer later on

Josh, Northwich, via text on 81111: "Just want to say gutted about Kubica missing the season was looking forward to seeing him challenge for race victories. Get well soon Robo!"

1345: Many of you asking why there's no TV coverage of testing. Quite simple really. Bernie Ecclestone's Formula 1 Management (FOM) company - not the BBC - provide the pictures in this sport and obviously they don't feel that broadcasting the test events would make economic sense.

1340: The track is clear, red turns to green, here we go...

1335: My hope of three hours' uninterrupted action lasted all of half an hour. We have a RED FLAG after Kobayashi stops on the track at Turn 5. A second crane-lift of the day in progress, but no sign of an oil spill. Word is the Sauber driver was testing the limits of his fuel tank, not uncommon for teams during testing.

BBC sports news correspondent Dan Roan on Twitter: "F1 supremo Bernie Ecclestone tells me now "hopeful" Bahrain GP will go ahead - exclusive interview available across BBC outlets now"

1328: A Bahrain update coming right at ya...

F1 Fanatic on Twitter: "Summer has arrived in Barcelona, track temp of 29.4 degrees & air temp 15.7. More fans have arrived now and the paddock is very busy. Karthikeyan has run the most laps, total of 58. Making up for lost time, Schumi has run the least, just 13"

anku_thakur on Twitter: "Reliability issues with the car will a be HUGE problem at the start of the season. And the signs aren't good for Williams and Mercedes"

1325: Time for Michael Schumacher to get some proper laps under his belt. The seven-time world champion has said he's "slightly concerned" about the pace of his new Mercedes challenger, while reliability issues have also been mentioned. Schumacher manages his quickest time of the day - a 1:27.512 - during a three-lap stint before heading back into the pits. Alonso, Alguersuari, Button, Vettel and Barrichello remain the top five.

Mercedes GP on Twitter: "Lunch break over and it's back to the action in Barcelona... Michael is back on track."

1315: No shame in admitting I was slightly overwhelmed by the sheer volume of comments this morning, but keep 'em coming and I'll endeavour to pick out as many good'uns as I can. Normal procedure: get in touch via the Twitter hashtag #BBCF1 contact me directly @bbcsport_david and we'll try to get your question answered. Alternatively, you can text me on 81111 (UK).

1310:Sun is in the sky oh why oh why would I want to be anywhere else? Because London's cold and actually the sun isn't in the sky, while Barcelona's warm and the sun certainly is in the sky. All of which makes for a dry track and quick times. Mr Alonso wowed his home crowd with a lap of one minute, 25.485 seconds before almuerzo, but who will head the field come 1600?

1300: Anybody there? If the deluge of comments in my mailbox is anything to go by, the answer to that is a resounding 'yes'. Do you people not take lunch breaks? Enormous amounts of chat now doing the rounds in relation to Bahrain. More on that soon. But for now it's back to Barcelona and day one of testing at the Circuit de Catalunya. Three hours of (hopefully) uninterrupted action starting... NOW!

1215: And time for me to replenish too. Back in a bit for what should be a cracking afternoon.

1210: Lunch being taken as we speak, cars back on the track at 1400 local time (1300 GMT). Here's how we stand: Alonso (one minutes, 25.485 seconds), Alguersuari (1:26.117), Button (1:26.117), Vettel (1:36.640), Barrichello (1:27.447), Schumacher (1:27.661), Kovalainen (1:30.464), D'Ambrosio (1:32.068), Karthikeyan (1:32.396), Kobayashi (1:36.264), Heidfeld (1:44.324).

Tim, Bristol, via text on 81111: "Agree with Jake, Bahrain and its people have far more pressing issues to deal with than an F1 race. Cancel it now so the teams know nice and early and have an extra testing session in its place."

Alan, Nantwich, via text on 81111: "If the test and race in Bahrain is cancelled I think the teams should have a four day test in Barcelona finishing off with a short notice non-champion ship race for fans. Being non-championship individual teams could decide if they participate or not."

1204: The lunch break has been called. Good news for me - my stomach's rumbling like a Ferrari engine.

Renault GP on Twitter: "A few issues have kept Vitaly in the garage this morning. He'll be back out after the lunch break at 14:00."

1200: Barrichello's Williams is crane-lifted on to a truck and whizzed back to the pits under a blanket. Seems a good point at which to stop for lunch but no decision from track officials just yet.

BBC F1 presenter Jake Humphrey on Twitter: "For those asking, no news on the running of the Bahrain GP. It's not important given the context. I couldn't imagine being there at present"

1155: Uh oh. RED FLAG. Barrichello comes to a stop at Turn 7. "No oil reported on the track, which is a relief to all of us," says Holty.

BBC Sport's Sarah Holt on Twitter: "By the way, Tonio Liuzzi is due to arrive in Barcelona later today with the idea that he will test for Hispania on Saturday. Liuzzi is looking for a drive for 2011 and Hispania are still looking for a driver. Could be the perfect match?"

Simon, London, via text on 81111: "Cold and wet start to the first day of testing and two new tyre compounds from Pirelli - this is going to be a great day of perpetually falling lap times :)"

1149: Alguersuari up to second with a 1:26.117 in his Toro Rosso. Various weather sites are suggesting it's slowly warming up in Barcelona so we should see some even quicker times as the afternoon progresses.

BBC Sport's Sarah Holt in Barcelona: "Team representatives are due to sit down at the Circuit de Catalunya this evening and the Bahrain test is likely to be top of their agenda. The final pre-season test is scheduled to be held in Bahrain between 3-6 March with the Bahrain Grand Prix opening the 2011 season one week later. The test - and race - are now in question because of the political unrest in the Gulf state. An F1 team insider told me they would prefer to stay in Barcelona for the final test and it will be up to the teams, with guidance from Bernie Ecclestone's Formula 1 Management (FOM) company, to decide whether that would be the best option. Apart from anything else, the teams need to make logistical decisions because the first shipment of freight is due to leave Barcelona for Bahrain next Wednesday. A spokesperson for the Circuit de Catalunya says Red Bull have already asked on behalf of all the teams if the track would be available to stage the fourth test if necessary. And the answer is, yes."

1143: Right on cue, here's our Holty with an update re Bahrain...

seperatesunsets on Twitter: "Are there any specific contingency plans through force majeure of a Grand Prix or testing session?"
We're trying to get answers to that very question. Click here for the latest on the Bahrain unrest.

1135: A little quiet out there right now, Vettel heading into the pits to leave Button and Alguersuari as the only men on the track. High time for a banana me thinks, back in a mo.

Jonny, Belfast, via text on 81111: "Are Hispania using their new car today, or are they still using their 2010 car?"
Still in the 2010 model (see 0924)

1129: Oh no he doesn't... Vettel jumps above Alguersuari and into third after going round in 1:26.640.

1128: Vettel and Schumacher post their slick-tyre times of the day to move into the top five as Alonso extends his advantage at the head of the field to 0.880 seconds with a lap of 1:25.485. The Spaniard leads from Button and Alguersuari.

No pics from today yet but Alonso will look something like this

F1 Fanatic on Twitter: "For any Alonso fans out there, (there must a few even in hiding!) you will be pleased to know his dreadful beard has gone."

1115: Talking of Alonso, the Spanish two-time world champion responds to Button's flying lap with one of his own... and it's a 1:25.597, which puts him fastest by 0.768 seconds. The grandstand must've loved that. Get your white handkerchiefs out.

1110: Seems most - if not all - the drivers are now on slicks and boy the times are beginning to drop. There's a big crowd at Circuit de Catalunya today - there always is when Fernando Alonso's in town - and they've just seen Jenson Button soar to the top of the timesheets with a lap of 1:26.365 in his new MP4-26.

burwellian on Twitter: "Re 1040, by who? If you're playing a song called Barcelona, it has to be Freddie Mercury & Montserrat Caballe surely!"
Hard to argue with that, I must admit.

1100: Slick tyres and a slick lap - Alguersuari is the first man to go under 1:30.000 as he tops the timesheets with a 1:29.957. And then lowers that to 1:29.197.

Force India on Twitter: "Lap times are steadily coming down at Barcelona, old top times have been blown away!"

1055: Crikey - Barrichello takes advantage of the ever-developing dry line to register a lap of one minute, 30.045 seconds. That's 4.265 seconds clear of his nearest challenger, D'Ambrosio (1:34.310). We know precious little about teams' fuel loads, tyres and strategies, but that's a proper time.

Heikki Kovalainen on Twitter: "Testing underway in Barcelona, damp track this morning gettin feel for the intermediate tyre, now drying so soon on slicks! All kool!"

Team Lotus technical chief Mike Gascoyne on Twitter: "Track starting to dry and times falling. Currently stopped fixing a small water leak, ready to go soon."

BBC Sport's Sarah Holt in Barcelona: "Vitantonio Liuzzi is expected to arrive in Barcelona later today with the hope of testing for Hispania this weekend. Hispania are still looking for a second driver for 2011 and the 29-year-old Italian is still looking for a drive. The Spanish team are understood to be keen on offering Liuzzi a place alongside Indian Narain Karthikeyan. Liuzzi is on the market because Force India decided to promote Scot Paul di Resta to a race seat even though the Italian still had a contract to race for the team in 2011. Force India have since been trying to negotiate a settlement with Liuzzi. After being passed over in favour of Nick Heidfeld as the injured Robert Kubica's replacement at Renault, it is a case of watch this space as Liuzzi attempts another F1 comeback."

1049: As the lyrics say, "every time I hear this tune I just start drifting away". And with more than five hours of this text commentary still to go, that isn't good news. Come on, Ornstein, wakey wakey. Now then, Vettel's back out on the track but it's still relatively chilly so 't expect astonishing times just yet. Kobayashi still leads the way but Virgin Racing rookie Jerome D'Ambrosio is up to second with a 1:36.411. Good work from the Belgian former GP2 man.

1040: Is it wrong that I just caught myself singing 'Barcelona' by D Kay and Epsilon out loud when everyone else in the office is working in silence? Not usually a great fan of drum and bass but I must say it's a super tune about a super city.

BBC Sport's Andrew Benson: "To answer your questions about tyres, the allocation is exactly the same as last year - two specifications of dry-weather tyre, both of which must be used during the race if it's dry, and a driver has access to 11 sets of dry-weather tyres, six of the harder 'prime', five of the softer 'option'. Full details here. How do Pirelli choose which two of their four types of dry tyres to take? Well, they pick the ones that are most suitable for the track. This decision will be based on circuit abrasiveness to a large degree - Barcelona, for example, is very abrasive, so needs harder tyres, while Monaco is much less so, so you need softer tyres there. But this year the decision will also be based on what sort of racing is likely to be provided. Pirelli have been asked to provide tyres that go off quicker, so requiring more pit stops and creating more entertaining action, such as in Canada last year."

1033: vikkikf and Kate_wise, I have answers for you...

1030: Remember, these are still very much wet times we're seeing. Mark Webber's pole-setting lap at last season's Spanish Grand Prix (on this very track) was 1:19.995, while the quickest time in the race was a 1.24.828 - also set by the Australian Red Bull driver as he stormed to victory. Even if drivers were running heavy fuel loads and hard tyres today, you wouldn't expect to see a dry time much slower than 1:30/31. So we're still a good four or five seconds away from a normal dry time - and that's with a full tank.

1020: Out comes reigning world champion Sebastian Vettel for his first flying lap of the day. How quick will he be? Here we go... 1:39.959. It's the fourth-fastest time so far. Oooh but he's just been bumped down to fifth, Kobayashi of Sauber leapfrogging Schumacher with a 1:36.264.

1016: And seven-time world champion Schumacher announces his arrival with a lap of one minute, 37.466 seconds. It was his first flying lap and it puts him top of the timesheets, 0.963 seconds in front of Button. The German goes straight back into the pits.

1014: Schumacher at last gets an installation lap under his belt, so the final car to hit Barcelona's Circuit de Catalunya today will be that of Britain's Paul di Resta in his Force India.

1012: A couple of big laps from a couple of big boys. Barrichello shoots back atop the timesheets with a 1:39.162, only for Button to immediately usurp him with a 1:38.429 and then head into the pits. Barrichello completes his nine-lap run with an average time of 1:41 flat. The Brazilian is currently second-fastest, 1.979secs clear of Alguersuari, with Kovalainen fourth and Karthikeyan fifth.

Kate_wise on Twitter: "This may be a stupid question - but how do Pirelli go about choosing option & prime tyres? Do f1 teams vote?"
It's not a stupid question and I'll add it to Andrew's pile!

vikkikf on Twitter: "With the higher rate of degradation on the new Pirelli tyres, will there now be a higher allocation of tyres per race?"
That's one for our resident F1 expert Andrew Benson. He's logging in next to me as we speak, so I'll get back to you shortly.

Don, Birmingham, via text on 81111: "As Bahrain is notoriously low attendance, would it make a difference if cancelled? Surely if Bernie is speaking about it there is some weight there. Would there be merit in having an emergency alternate track for any unfortunate world events, like a Paul Ricard?"

0950: Alguersuari (1:40.408) still the man to beat but Kovalainen (1:41.115) is snapping at his heels and Button (1:42.000) sits 1.592 seconds off the pace after a few flying laps. All those driving today are due to stay in their cars tomorrow - with the exception of seven-time world champion Michael Schumacher, who'll be replaced by Nico Rosberg in the new Mercedes. Vitaly Petrov is scheduled to take over the Renault seat from Nick Heidfeld for a spell this afternoon.

Brian, Winsford, via text on 81111: "Can't they switch Bahrain to Abu Dhabi, they near each other, so won't be a logistics issue, and a better track."
Hold on, I'll just give Bernie a shout...

Rubens Barrichello on Twitter: "Barcelona test underway and I already being tested today at 6AM from the WADA guys...the anti dope test could be a little later hehe."

0938: The Bahrain situation is just one of numerous talking points as the 2011 season nears. From team orders to tyres, curfews to Kers, F1 drivers to F-ducts - this year promises to be another belter. And we at BBC Towers can't do any of it without you. So start as you mean to go on and be sure to have your say. You can contribute to these text commentaries via the Twitter hashtag #BBCF1 but if you have any specific questions why not contact me directly @bbcsport_david and I'll try to get back to you with an answer. Unless, of course, you're not into all this social media malarkey. In which case, pop me text message on 81111 (UK).

BBC F1 presenter Jake Humphrey on Twitter: "Bahrain has bigger things to concern it than F1 at present it seems. Remember what's happening there is real life. The people of Bahrain have have given us the warmest welcome for the past couple of years. We should be thinking of them rather than sport."

0924: As Sarah points out, Hispania are still using last year's vehicle. In fact, they're the only team still running a 2010 car. Their newbie is due to hit the track at the final pre-season test in Bahrain on 3-6 March - but unrest in the Gulf state means both that and the season-opening Bahrain Grand Prix could be cancelled. More news as and when we get it.

Team Lotus technical chief Mike Gascoyne on Twitter: "Damp and cold start to testing here in Barcelona. First running in wet conditions for us this year."

BBC Sport's Sarah Holt in Barcelona: "Hello again. The car engines and I were in unison this morning as we cleared out throats and tried to warm up in the chilly Barcelona air. It was a rather cool 5C when the session began an hour ago but the sun is beaming and I have felt safe to take my coat off at media HQ. After a quiet first hour, the media fray are slowly arriving and there are, as you would expect, lots of whispered questions about the fate of next week's Bahrain test in light of the current unrest in the island state. Here in Barcelona, all the cars have made their first forays on track with the exception of Mercedes although Red Bull's Sebastian Vettel and McLaren's Jenson Button have only nipped out for installation laps so far. Hispania have also resumed testing in their 2010 car after skipping last week's Jerez test."

0914: Back to the circuit we go and it's Jaime Alguersuari who now tops the timesheets at his home track. The 20-year-old Catalan, who became the youngest ever F1 driver at the 2009 Hungarian Grand Prix, goes round in 1:41.698 to lead by 1.322 seconds from Rubens.

0907: And one last bit from Hembery... "Barcelona is a track that both ourselves and all the teams are very familiar with, so I'm sure we will come back with plenty of information once more. Once more, the track characteristics are quite different to the two circuits that we have tested at before, which enables the teams to experience the behaviour of our tyres under a wide range of circumstances: something that will be crucial to formulating race strategies as the year goes on."

0905: More from Pirelli. Here's their motorsport director Paul Hembery: "We managed to collect a lot of data from our test with all the teams in Jerez and we've been very busy evaluating it to see what we can learn. What's interesting is that the emphasis during testing is changing: as the teams get up to speed with their new cars the work has become much more focussed, with some longer runs and potential race set-ups being evaluated. We've also got some evolutions of the supersoft and soft tyres, which was always part of our development schedule."

0900: Pirelli, I can confirm, have brought to Barcelona an evolution version of the supersoft and soft compound 'PZero' tyre, as well as the medium and hard compounds. "The modifications have been incorporated following feedback from the teams and from the extensive data accrued by Pirelli's engineers," read a statement. "This will be the final opportunity that the teams have to sample all four dry tyres from the Pirelli range - supersoft, soft, medium and hard - as from the Bahrain test onwards only the compounds that have been selected as the prime and the option for the races will be provided."

0858: Lots of interest in how the Pirelli tyres will perform this season. The Italian manufacturer is, of course, taking over from Bridgestone as the sole supplier in 2011. Experts say the Pirellis have quicker rates of degradation - the supersofts going off after as little as one lap - and that should bring an end to the one-stop strategy. Good news for the pit-stop junkies out there.

0850: Ferrari's Alonso and world champion Sebastian Vettel of Red Bull are back in the pits. Various tyre selections this morning - some of the drivers on full wets, others on intermediates. The damp track has made for some fairly slow lap times so far, but it's drying out now so we can expect a few quickies.

Ferrari on Twitter: "Today's programme includes mainly tyre and set-up testing. The track still wet after yesterday's rain"

0845: BANG. Brazilian veteran Rubens Barrichello goes quickest with his first flying lap. It's a 1:44.769 and it's put him top of the timesheets. Kovalainen second, 3.297secs adrift.

0842: ...until, that is, Heikki Kovalainen produces a flying lap of 1:48.413 for Lotus Racing. Nick Heidfeld, who will replace the injured Robert Kubica for Renault this season, and Ferrari's two-time world champ Fernando Alonso complete the top five. Jenson Button, meanwhile, completes McLaren's first installation lap. Mercedes and Michael Schumacher the only team/driver yet to hit the Circuit de Catalunya today.

0837: We have our first lap time of the morning and it's set by Kamui Kobayashi, an effort of one minute 51.803 seconds in his new Sauber. He soon gets it down to 1:46.833, almost five-and-a-half seconds quicker than second-place Narain Karthikeyan of Hispania.

Mercedes GP on Twitter: "We're pleased to announce that Bob Bell will be joining the team as Technical Director from 1 April 2011. Ross [Brawn, team principal] said... 'Bob's appointment is a key step in the strengthening of our excellent technical team.' Bob commented: 'It will be a privilege to be a part of such a strong and determined organisation.'"

0825: Heavy rain on Thursday has made for a damp surface, so the teams could get their first taste of Pirelli's wet tyres today. All 12 teams are in attendance at this, the final European test before the season-opening Bahrain Grand Prix on 13 March. That said, there is talk of the last test - due in Bahrain on 3-6 March - being switched to Spain because of the current unrest in the Gulf state. There is even concern that the Grand Prix could be cancelled.

Mercedes GP on Twitter: "Just 5 degrees on the way into the circuit this morning but the skies are clear and looks like it will be a nice day. Just a reminder that our schedule for this test is: Michael - Friday/Monday, Nico - Saturday/Sunday."

0815: Welcome to our coverage of the penultimate pre-season test before the 2011 Formula 1 season. The venue? Barcelona. The track? Circuit de Catalunya. The weather? Chilly but clear, sunshine in the skies. Day one of four. Let's get it on.

0810: A couple of months ago someone told me there was a major sporting event involving Barcelona this week. Monday came and went - nothing. Tuesday passed without mention and as for Wednesday, there was a fairly important football match but that's about it. Thursday? Nope. Ah, thank goodness for Friday...