07:54 Good morning and welcome to AUTOSPORT's Live coverage of the final day of pre-season testing in Barcelona.

07:56 It's a fairly overcast morning, air temp is 8.3C. A far cry from one forecast we saw earlier in the week predicting a top of 21C.

07:57 BEN ANDERSON, LAWRENCE BARRETTO and MITCHELL ADAM will bring you today's action. But we must confess to being a little bit scarred after our hotel insisted on playing 'Get Away' by Lenny Kravitz every other song over breakfast.

07:58 But we'll push on. We're about two minutes away from the green flag. If you missed yesterday's news, Lewis Hamilton topped the times and gave the rest of the field plenty to think about...

Barcelona F1 test: Mercedes tops penultimate day with Hamilton

07:58 Here's who we can expect to see on the Circuit de Catalunya today:

Mercedes - Rosberg
Red Bull - Ricciardo
Williams - Bottas
Ferrari - Vettel
McLaren - Button
Force India - Perez
Toro Rosso - Verstappen
Lotus - Maldonado
Sauber - Nasr

08:00 And we're off. We can hear plenty of engines down in pitlane heading straight out.

08:01 Nasr, Rosberg, Vettel and Bottas are straight out of the box...

08:02 Maldonado heads out in the Lotus to join the party.

08:04 Vettel heads back to the pits, but Nasr cracks on and clocks the opening time of the day - 1m45.530s.

08:04 If Nico ever drove a Newey-designed car and won a race, we'd like to hope he'd yell "yo Adrian we did it" over the radio.

@nico_rosberg "ready for another marathon. preparing like a prize fighter... @MercedesAMGF1 #TestBarcelona"

08:06 Rosberg pits after a couple of installation laps, as does Bottas and Maldonado.

08:07 Ricciardo peels into the pits after his installation laps while Verstappen heads the other way in the Toro Rosso.

08:09 So within the first nine minutes, we've seen eight drivers as Perez heads out in the Force India - just Button has yet to make an appearance. Plenty of time, though. Plenty.

08:10 Perez takes over from Nico Hulkenberg, who logged an impressive 235 laps in the new car in the day-and-a-half since it first appeared just before lunch on Friday.

Reliability of new Force India F1 car surprises Nico Hulkenberg

08:16 After the initial run of installation laps, Maldonado and Vettel are back on track.

08:17 Despite setting a soft time faster than what Williams and Ferrari achieved on super-softs yesterday, Lewis Hamilton insists it's not all smooth sailing at Mercedes.

Barcelona F1 test: Lewis Hamilton puzzled by Mercedes set-up

08:18 Vettel, 1m31.501s, and Nasr, 1m46.530s, have set the token first laptimes of the day.

08:21 On his first lap of the day, Rosberg drops a 1m27.573s. Vettel, meanwhile, has improved to a 1m29.863s.

08:21 You might also have noticed that Hamilton is still carrying #44 on his Mercedes even though he had the option to take #1 as champion.

He's been explaining why:

Hamilton rejects #1 as 'irrelevant'

08:23 On unmarked Pirellis, his team-mate Rosberg improves to a 1m25.678s.

08:24 Perez has posted his first laptime aboard the VJM08, 1m28.739s.

08:25 As Rosberg improves again with a 1m25.492s.

08:29 Here's a pic of Perez during his first run in the new Force India, he's now completed six laps.

08:31 Half an hour in, and as Rosberg continues a long run, here's a look at the lap counts:

Rosberg - 11
Nasr - 8
Perez - 7
Vettel - 5
Bottas - 4
Maldonado - 4
Verstappen - 4
Ricciardo - 1

No sign of Button yet.

08:33 Rosberg's now back into the pits after that 11-lap run. He spent the bulk of it in the 1m26s bracket.

08:34 For those following on the mobile app, here's a look at the early leaderboard:

1 Nico Rosberg Mercedes 1m25.492s
2 Felipe Nasr Sauber 1m27.963s +2.471
3 Sergio Perez Force India 1m28.682s +3.190
4 Sebastian Vettel Ferrari 1m29.863s +4.371

08:43 Though Jenson Button hasn't been out of the McLaren garage yet, he has been congratulating his sometime Jaguar F1 test driver mate James Courtney on a great start to the V8 Supercars season in Adelaide:

"@jcourtney Mate congrats on an Epic win! #22"

Here's how Courtney triumphed at the much-loved old Australian GP venue:

Courtney leads V8 Supercars after Adelaide win

08:46 Rosberg and Perez are currently out on track, but otherwise it's fairly quiet at this moment in time. Like the first hour of most test days, it looks a lot like this.

08:49 Rosberg's on a run on the medium tyre, improves the fastest time we've seen so far today to a 1m25.277s.

08:55 Ricciardo joins the fun to set his first lap of the day, a 1m27.019s.

08:55 It's briefly good enough for second, before Bottas logs a 1m26.718s. Vettel, meanwhile, has improved to 1m28.247s.

08:58 Rosberg pits to end another 10-lap stint on the mediums, he was lapping consistently in the 26s.

08:59 Ricciardo is on unmarked Pirellis, and has improved to a time of 1m26.587s. Bottas is on mediums.

09:00 @McLarenF1 "Bit of a delay with today's programme, the team are running some system checks, but hope to be out later this morning…"

09:01 At the end of the first hour, here's how the times look:

1 Nico Rosberg Mercedes 1m25.277s
2 Daniel Ricciardo Red Bull 1m26.587s +1.310
3 Valtteri Bottas Williams 1m26.718s +1.441
4 Felipe Nasr Sauber 1m27.353s +2.076
5 Sergio Perez Force India 1m28.016s +2.739
6 Sebastian Vettel Ferrari 1m28.805s +3.528

09:03 And the lap tally, with Button yet to appear.

Rosberg - 22
Bottas - 16
Perez - 15
Vettel - 14
Nasr - 13
Ricciardo - 1
Verstappen - 7
Maldonado - 6

09:06 This brief pause in activity is the perfect time to tell you about CRAIG SCARBOROUGH's latest technical feature, picking out the highlights from the new pieces each team has brought to Barcelona.

Barcelona F1 test technical overview

09:13 Currently only Rosberg, who has just left the pits for another run on the unmarked rubber, and Verstappen on track. The latter has now recorded several times, his best is a 1m28.422s.

09:14 And Rosberg lowers the benchmark again, clocking a 1m25.186s.

09:15 And we've now got red flag.

09:15 It'll be Ricciardo, stopped at the end of pitlane having just left his garage.

09:18 It's the third stoppage in four days for Red Bull.

Kvyat caused a red flag in similar circumstances on Thursday but got going again quickly, then came to a halt at Turn 1 on Friday as a "precautionary stop on track to check a hydraulic sensor".

09:19 The Red Bull's being pushed back down pitlane by the team, not even bothering with the recovery vehicle.

09:20 Our tech man CRAIG SCARBOROUGH was on the scene.

09:22 Off we go again, Vettel, Rosberg and Maldonado have all headed out, with the Red Bull back in its garage.

09:25 Vettel improves to a 1m26.639s, while Maldonado logs his first time of the morning, 1m29.185s.

09:29 @pirellisport "We've had a few questions about the unmarked tyres. They are prototype mediums. Winter hards have already all been used. #F1BarcelonaTest"

09:31 A group of guests on what seems to be a circuit tour are currently in the media centre. They look like school kids on an excursion.

09:33 On track, Rosberg, Bottas, Nasr and Verstappen are circulating.

09:34 @pirellisport "In terms of performance, there's no difference between prototype mediums and 2015 mediums. Some different materials, that's all #F1"

09:34 Bottas has now pitted, while Verstappen has just gone to second with a 1m26.267s. Believe he is on softs, will check next time he comes past.

09:36 Verstappen's time was indeed set on softs.

09:36 Seems as good a time as any to give you an update on the times:

1 Nico Rosberg Mercedes 1m25.186s
2 Max Verstappen Toro Rosso 1m26.267s +1.081
3 Valtteri Bottas Williams 1m26.440s +1.254
4 Daniel Ricciardo Red Bull 1m26.587s +1.401
5 Sebastian Vettel Ferrari 1m26.638s +1.452
6 Felipe Nasr Sauber 1m27.353s +2.167
7 Sergio Perez Force India 1m28.016s +2.830
8 Pastor Maldonado Lotus 1m29.185s +3.999

09:37 And the lap count:

Rosberg - 34
Vettel - 24
Nasr - 24
Bottas - 22
Verstappen - 18
Perez - 16
Maldonado - 14
Ricciardo - 10

Still no sign of the McLaren, 90 minutes into the day.

09:40 If you've managed to avoid pinches and punches, you might not realise that today is the 1st of March.

So for no real reason other than that, here's a pic of the last time a March was 1st in Formula 1, Ronnie Peterson winning the 1976 Italian Grand Prix at Monza.

09:46 Maldonado and Verstappen had been sharing the track, but Maldonado has just brought the Lotus back into the pits. It's all Verstappen's.

09:51 Max gets a mention in another response we've kept up our sleeve from Friday's #askKarunF1 chat with KARUN CHANDHOK. You can read the full feature here:

Chandhok answers your testing questions

@Chr153van5BRFC asks: "What would you say to any young and upcoming driver that wants to make F1?"

KARUN CHANDHOK: "Knowledge is like gold dust in this game. It's not just about driving round and round in circles. There's a lot of other things, there's the politics, there's the business, there's the commercial side.

"There's a lot of things you need to understand about how the sport works before you go ploughing through your second mortgage to do a season in Formula 4. The one thing I would always say to drivers is be realistic.

"You have to dream – it's nice to chase that dream, but you have to be realistic and really be true to yourself. Do you have the talent, do you have the budget, and if not, why are you wasting your money?

"People like Max Verstappen prove that there is still a place for talent to come through. But unlike in the past, it takes an extraordinary talent to be able to get to F1 in that way. I don't think it matters who his dad is – he's just supremely fast. Jos seems to have brought him up as a level-headed chap, which he really needs to be. All credit to them."

09:54 Verstappen has now pitted, he's done 21 laps for the day. We were just having a look for a photo of him on LAT, and spotted BEN ANDERSON's sneaky photobomb during Max's media session on Friday.

09:56 With Max back in the pits, we have Vettel, Nasr, Perez and Maldonado on track nearing the end of the second hour.

10:00 @redbullracing "After a good start on the final day of testing, the #RB11 has had an ERS problem. The Team are looking into it. #F1"

10:03 With that bit of news from Red Bull, here's what you need to know at the end of the second hour:

* Rosberg comfortably on top after longer runs on mediums
* Verstappen P2 after soft tyre lap
* Ricciardo stops at the end of pitlane with ERS problem to cause red flag
* No sign of McLaren due to "system checks"

10:04 Here's the times, for those of you reading on a mobile device:

1 Nico Rosberg Mercedes 1m25.186s
2 Max Verstappen Toro Rosso 1m26.267s +1.081
3 Valtteri Bottas Williams 1m26.440s +1.254
4 Daniel Ricciardo Red Bull 1m26.587s +1.401
5 Sebastian Vettel Ferrari 1m26.639s +1.453
6 Felipe Nasr Sauber 1m27.353s +2.167
7 Sergio Perez Force India 1m28.016s +2.830
8 Pastor Maldonado Lotus 1m28.272s +3.086

10:06 And the lap count:

Nasr - 37
Rosberg - 34
Vettel - 30
Verstappen - 27
Maldonado - 27
Perez - 23
Bottas - 22
Ricciardo - 10

10:07 Bottas has just gone to the top on the unmarked, prototype mediums. 1m25.009s is the new time to beat.

10:09 Bottas and Nasr, the latter on a longer run, had been the only two cars on track but they've now pitted. Vettel has headed out.

10:12 The Ferrari driver sets his best lap of the day, a slight improvement to 1m26.501s.

10:18 The sun's becoming slightly more visible and the air temperature is up to 12.5C. However there's plenty of cloud still around as this pic of Rosberg - who's back on track - shows.

10:19 Bottas has improved ever so slightly again, gets down to a 1m25.076s.

10:21 Bottas pits, leaving Rosberg, Verstappen, Nasr and Perez on track.

10:24 Perez jumps up to a 1m26.414s in the Force India. He's put 25 laps on the board so far today.

10:26 Sergio was on the softs.

10:31 Bottas throws on a set of softs and goes fastest - it's a 1m23.859s.

10:33 He duly returns to the pits, leading Rosberg - on mediums - and Nasr on track. Nasr is in the middle of a very long run, could be his second race sim of the week.

10:36 Nasr has just completed his 50th lap of the day. He's circulating in the 29s on the medium Pirelli.

10:41 Here comes a super-soft run from Bottas.

10:43 It's a 1m23.063s from Bottas.

10:44 That's two-tenths faster than Massa and Raikkonen went on the super-soft in the hour before lunch yesterday. But 0.041s slower than Hamilton went on the softs.

10:45 The completion of Bottas' qualifying run means the circuit is empty. You could call it Daniel Riccarless.

10:48 Perez returns to the track, to move us out of 'dad joke' territory.

10:49 @WilliamsRacing "After a run on the @pirellisport red rubbers @ValtteriBottas pits on top of the time sheet"

10:51 Having another run on the softs, Perez improves his best time to a 1m26.074s.

10:51 Here are the full times, for those of you on a mobile device:

1 Valtteri Bottas Williams 1m23.839s
2 Nico Rosberg Mercedes 1m25.186s +1.347
3 Sergio Perez Force India 1m26.074s +2.235
4 Max Verstappen Toro Rosso 1m26.267s +2.428
5 Sebastian Vettel Ferrari 1m26.501s +2.662
6 Daniel Ricciardo Red Bull 1m26.587s +2.748
7 Felipe Nasr Sauber 1m27.353s +3.514
8 Pastor Maldonado Lotus 1m28.272s +4.433

10:57 A few people are opposite us in the grandstand today, enjoying a bit more sunshine than this morning. However, with Perez pitting, they don't currently have cars to watch on track.

Other than the little go-kart track on the exit of the final corner.

11:00 We are, though, approaching what has been a busy hour over the last two days - the final hour before lunch.

Other than when the rain arrived on Thursday, many teams have used this hour to undertake qualifying simulations on the soft and super-soft Pirellis. It's when Massa and Raikkonen set their fastest times yesterday, for instance.

Air temp is up to 13.8C, track temp is 24.4C and if it helps you prepare for the hour ahead, there's 63 per cent humidity.

11:02 Here's the lap count from the first three hours of running.

Nasr - 52
Rosberg - 45
Perez - 37
Bottas - 34
Perez - 37
Vettel - 36
Maldonado - 27
Ricciaro - 10

11:02 The day's busiest driver, Nasr has headed out again.

11:07 The headlines as we enter the final hour of the morning session:

* Bottas fastest on super-softs
* Rosberg's time set on mediums
* ERS problem stops Ricciardo and causes red flag
* McLaren unsighted

11:08 The first of the pre-lunch movers is Nasr. He goes second-fastest on the softs with a 1m24.852s.

11:11 Rosberg's back out on the medium, Perez on the soft and Maldonado on mediums.

11:14 Bottas is completing another super-soft run.

11:16 No improvement from Bottas on that lap. Nasr, though, does a 1m24.715s on the softs, his best time of the day.

11:18 Actually, scratch that on Bottas. Turns out he's on the orange hards, not the red super-softs. Mistaken tyre identity from afar.

11:23 Still no sight of McLaren today. The Australian Grand Prix will have been run and won this time in two weeks, they desperately need to complete some substantial running this afternoon.

Red Bull, meanwhile, continues to work away on returning Ricciardo to the circuit after he stopped earlier.

11:25 We've got one last social debate we're keen to get your views on in our lunchbreak today, and it's an obvious one with two weeks before Melbourne...

We want you to tell us your favourite F1 season-opener.

Which first round of a season brought you must excitement, or contained your favourite surprises?

Let us know your choice and reasoning via the hashtag #autosportf1 and we'll publish a selection of the best in AUTOSPORT Live over lunchtime.

11:28 Vettel has broken the on-track silence by heading out for a run on the soft rubber.

11:29 He improves, marginally, to a 1m26.182s.

11:29 If McLaren fans feel in need of some comfort as we still await the appearance of the Honda-powered car today, Kevin Magnussen has been reiterating the team's belief that the new chassis has at least cured all the 'peaky downforce' problems of last year's car:

Magnussen: McLaren has cured 2014 chassis problems

11:32 Vettel finds a bit more time, turns a 1m25.552s.

11:32 Nasr has also improved, on the super-soft, he's now done a 1m24.023s.

11:37 Nasr pits after that run, leaving Vettel and Perez alone on track with just over 20 minutes to go until the lunch break.

11:38 Perez has just gone third-fastest, with a 1m25.113s.

11:41 That time from Perez was done on the super-softs.

11:41 Vettel is running the softs, while Nasr is back out on the super-softs and Rosberg on the hards.

11:47 Rosberg continues to pump in the times on the hards, the German currently lapping in the low 1m27s.

11:52 With just under 10 minutes to go until the lunch break, we've still yet to see McLaren and Button.

11:53 Vettel rejoins the fray on the super-softs and goes second with a 1m23.469s.

11:55 The McLaren finally heads out!

11:56 McLaren had a sensor problem, which required the engine to be taken out, hence the delay.

11:57 Button heads back to the pits without setting a lap time.

12:00 The chequered flag is out which means it's time for lunch!

12:01 So Bottas tops the charts after the morning session. Here's a complete rundown:

1 Valtteri Bottas Williams 1m23.063s
2 Sebastian Vettel Ferrari 1m23.469s +0.406
3 Felipe Nasr Sauber 1m24.023s +0.960
4 Sergio Perez Force India 1m25.113s +2.050
5 Nico Rosberg Mercedes 1m25.186s +2.123
6 Max Verstappen Toro Rosso 1m26.267s +3.204
7 Daniel Ricciardo Red Bull 1m26.587s +3.524
8 Pastor Maldonado Lotus 1m28.272s +5.209
9 Jenson Button McLaren No time

12:02 And here's the lap tally:

Nasr - 72
Rosberg - 69
Perez - 54
Vettel - 52
Verstappen - 49
Bottas - 45
Maldonado - 35
Ricciardo - 10
Button - 2

12:06 Ahead of our full report, here's a snapshot of the morning's headlines.

* Bottas fastest on super-softs
* Vettel second and Nasr third after late super-soft run
* ERS problem stops Ricciardo and causes red flag
* McLaren sensor issue restricts running to two laps

12:07 Plenty of suggestions coming in from you for your favourite F1 season-opener memories. Keep them rolling via #autosportf1 and we'll pick some of the best shortly.

12:07 After the session tonight, keep an eye out for our evening feature too - where our paddock team will be rated every team's winter.

12:14 Force India had another productive session, clocking up 54 laps with Sergio Perez at the wheel.

The team, who only ran its 2015 car for the first time on Friday, is in discussions with Bernie Ecclestone over financial support.

However, deputy team principal Bob Fernley insists it will compete in Formula 1's season-opening Australian Grand Prix.

Force India seeks payment advance

12:17 Here's the full round-up of and results from the morning's event, on a good day for Williams but a bad one (so far) for Red Bull and McLaren:

Bottas fastest on final morning

12:26 @MantsGuds was quick off the mark in our #autosportf1 call-out for your favourite F1 season-openers of all time, with a vote for Melbourne 2002:

"One of the craziest first turn incidents of all time and Mark Webber's debut points at home in a Minardi"

12:32 Melbourne's very first grand prix is @Rooooog's pick for F1's best season-opener:

"For me it's Melbourne 1996. Sensational debut of Jacques Villeneuve, major crash of Martin Brundle, Irvine P3 on Ferrari debut."

12:33 Don't forget, while we're highlighting readers' picks of favourite F1 season-openers during the testing lunchbreak, you can catch up on all the track action today so far in our midday report.

12:37 It's not just Melbourne races that have stuck with you as F1's best season-openers. @SimonkaJr remembers a Bahrain battle:

"Ferrari's resurgent 1-2 on the grid in Bahrain '06, just to be narrowly beaten by Alonso in a close and tense duel with Schumacher."

12:40 Motorsport News' archive-lurking editor KEVIN TURNER (@krt917) has got in on this debate too, picking "Moss winning in small Cooper" in Argentina 1958, but also "Prost's comeback, South Africa '82".

Alain Prost's drive to fight back from this puncture and win for Renault at Kyalami that year was one of his greatest. If you've always thought of Prost as a conservative tactician rather than an elbows-out charger, check that race out.

12:48 Our MN colleague also had a vote for the 1989 Brazilian GP as F1's best season-opener.

@TWRJag agrees: "Ferrari 640 so unreliable that Mansell books early flight home... and ends up winning the race."

A good omen for McLaren...?

12:51 Back to Melbourne races for @p__matt, who was among many around the world going "noooo!" when Juan Pablo Montoya lost it at Turn 1 with just a few laps to go in 2003.

"Oz '03 for me. It was the race that really got me into F1. Was gutted when JPM had that spin at the end that cost him the win."

12:54 @chrizb4's pick: "best opener 1993 Kyalami. Had everything: early spins, great racing, weather changes and a lunatic on track."

A Senna/Prost/Schumacher battle, last-gasp thunderstorm with everyone on slicks and a Ligier on the podium at a time when that was very, very uncommon... yep, South Africa 1993 was a great way to kick a year off.

12:58 But if this was a competitive vote, there would be a clear winner in our survey of F1's best season-openers: the 2009 Australian GP and Jenson Button and Brawn's fairytale win, which many of you have picked.

@Jori_Bremer sums it up: "Because from a near dead team in January to a 1-2 in Melbourne"

12:59 Thanks for getting involved, plenty of great stories there. Let's hope another chapter will be added in Melbourne in a fortnight when the 2015 season gets under way.

13:00 Here we go for the afternoon session.

13:01 To recap the morning...

Times:

1 Valtteri Bottas Williams 1m23.063s
2 Sebastian Vettel Ferrari 1m23.469s +0.406
3 Felipe Nasr Sauber 1m24.023s +0.960
4 Sergio Perez Force India 1m25.113s +2.050
5 Nico Rosberg Mercedes 1m25.186s +2.123
6 Max Verstappen Toro Rosso 1m26.267s +3.204
7 Daniel Ricciardo Red Bull 1m26.587s +3.524
8 Pastor Maldonado Lotus 1m28.272s +5.209

Laps:

Nasr - 72
Rosberg - 69
Perez - 54
Vettel - 52
Verstappen - 49
Bottas - 45
Maldonado - 35
Ricciardo - 10
Button - 2

Barcelona F1 test: Valtteri Bottas leads final morning for Williams

13:02 Morning pacesetter Bottas and the busiest man, Nasr, are the first out. And we can hear an engine below us in the Red Bull garage which is promising after Daniel Ricciardo's ERS problems.

13:06 Rosberg has headed out, as has Button. The latter needs a big afternoon after sitting out all-but the last five minutes of the morning.

13:10 Button completes a pair of laps and returns to the pits. Up to four for the day.

13:13 Red flag. Bottas and Maldonado are the only drivers yet to return to the pits.

13:14 Bottas has just ticked through the second timing sector, the Lotus must be stopped.

13:14 It's in the barriers at what looks like it could be Turn 5.

13:17 Turn 4 is where the Lotus is located.

13:25 The Lotus has now been cleared from the area and is on its way back to the pits on a truck. From the long CCTV angle it was impossible to tell how damaged the car - which appeared to have gone in front first - is.

Officials are currently repairing the tyre barrier at Turn 4.

Maldonado ended the morning eighth on the times, with 36 laps completed.

13:26 Off we go again.

13:27 Vettel and Button are the first men out following the restart.

13:28 Verstappen joins them.

13:30 Vettel's back in, while Rosberg has headed out.

And we have a completed laptime from Button, a 1m28.782s.

13:32 Button improves, to 1m28.391s, and we currently have the McLaren, Nasr, Perez, Rosberg and Verstappen on track.

13:33 An instant change to that list - Nasr has pitted but Ricciardo has headed out. The Aussie only turned 10 laps this morning after suffering an ERS problem.

13:36 Button has returned to the pits. He's now completed eight laps, one more than Thursday's seven, and enough for our colleagues at XPB to have taken a photo of the McLaren-Honda on track.

13:36 It's definitely feels warmer now than at any other time during this test, with air temperatures up to 18.9C and the track hiving around 31C. Sunglasses and short sleeves are certainly the order of the day.

13:40 Ricciardo improves to a 1m26.466s then pits. He, Perez and Button are the only men in the pits at the moment.

13:46 Button's back on track, has just turned a 1m26.832s.

13:49 This, the final afternoon of pre-season testing, probably marks the last time we'll see Red Bull's camouflage livery.

The black and white ditty has been a standout over the last month; a nice change of pace and also very easy on the eye. Could Red Bull give us the best of both worlds - building its regular colours on this design?

13:49 Button's time, by the way, came on the soft tyre.

13:50 @Lotus_F1Team "A bit of work in the garage after an off this afternoon. Currently assessing whether we'll return to the track."

13:51 And if you're wondering what Lewis is up to this afternoon...

@LewisHamilton "At the beach with Roscoe. I'm wishing you an amazing Sunday. #Monaco #bestdog #blessed"

13:52 If you missed the news earlier, Lewis has explained his rationale for sticking with #44 in 2015, rather than taking #1 as he's entitled to.

F1 champion Lewis Hamilton rejects #1 as 'irrelevant' and keeps #44

13:54 Back in Barcelona, Nasr, Perez, Verstappen and Ricciardo are lapping the circuit.

Afternoons have generally seen teams focus on long runs - including race simulations - on the medium and hard tyres. The track's currently the warmest it's been all week, so there's data to be gained over the coming hours.

13:56 That said, Ricciardo just completed his first run on the soft tyre of the test - having been sidelined this morning and stuck to mediums and hards yesterday.

He goes fourth-fastest, with a 1m25.103s.

13:57 That run would've been on Red Bull's morning schedule, before the ERS problems arose.

13:58 Red flag

13:58 Nasr, Perez and Verstappen are the cars on track

13:59 Perez is back in the pits and Nasr has just moved through the second sector, Verstappen is the odd man out

14:01 Showing road safety awareness beyond his years, Max has pulled off to the side of the track - the tight CCTV angle doesn't give us much help. We'd say Turn 12 if we had to have a go.

14:02 Looks like Verstappen won't be maximising his track time today...

14:11 After that third red flag of the day, we're away again.

14:14 Nasr, Ricciardo, Perez, Rosberg all head straight out.

14:15 The Toro Rosso, meanwhile, is back in pitlane. With less than three hours remaining, it could be the end of the team's winter programme.

14:16 Here's where everyone stands in terms of laps completed:

Nasr - 92
Rosberg - 82
Perez - 68
Verstappen - 68
Bottas - 63
Vettel - 54
Maldonado - 36
Ricciardo -16
Button - 13

14:17 The softs are Ricciardo's tyre of choice for his current run.

14:18 If you're following on the mobile app, here's a handy snapshot of the leaderboard:

1 Valtteri Bottas Williams 1m23.063s
2 Sebastian Vettel Ferrari 1m23.469s +0.406
3 Felipe Nasr Sauber 1m24.023s +0.960
4 Daniel Ricciardo Red Bull 1m25.103s +2.040
5 Sergio Perez Force India 1m25.113s +2.050
6 Nico Rosberg Mercedes 1m25.186s +2.123
7 Max Verstappen Toro Rosso 1m26.267s +3.204
8 Jenson Button McLaren 1m26.832s +3.769
9 Pastor Maldonado Lotus 1m28.272s +5.209

14:18 Ricciardo, on the softs, improves marginally to a 1m25.060s but stays fourth fastest.

14:20 Button is back out, too, and improves to a 1m26.323s, but stays seventh fastest with 15 laps on the board.

14:23 Button, who did that last lap on the softs, pits while Perez continues on the mediums.

14:27 Nasr becomes the first driver to clock up 100 laps today.

14:30 Ricciardo pits and rejoins on the softs.

14:31 Ricciardo improves first lap around, the Australian clocking a 1m24.638s, but he stays fourth, 1.575s off the pace.

14:34 Ricciardo pits, leaving Perez, Nasr and Bottas out on track.

14:43 Button moves up to sixth with a 1m25.994s, 2.931s off the pace.

14:44 Button pits, leaving Vettel and Nasr with the track to themselves.

14:45 @ToroRossoSpy: "We've had to stop due to engine problem. Max will have to wait before hopefully going out again."

14:46 Vettel is on a race simulation with the German's pit board reading L60 and counting down. He's currently running the medium tyre.

14:48 Vettel's last three laps have been in the low to mid 1m30s.

14:50 After a stroll around the paddock, we can confirm that the weather here in the sun is exceedingly pleasant. Current air temp is 18.2C, track temp 28.9C.

14:51 Lotus looked to have started the task of dismantling its hospitality unit - or removing something from the roof at the very least. Still no word from the team about whether they'll be back out following Maldonado's accident earlier.

14:57 Our colleagues from LAT were on the scene when Maldonado's Lotus returned to the pits a little earlier.

14:59 The pack up has also started over at Toro Rosso, with the team moving one of its trucks into position to start loading.

15:04 With two hours of winter testing remaining, here's how the times look:

1 Valtteri Bottas Williams 1m23.063s
2 Sebastian Vettel Ferrari 1m23.469s +0.406
3 Felipe Nasr Sauber 1m24.023s +0.960
4 Daniel Ricciardo Red Bull 1m24.638s +1.575
5 Sergio Perez Force India 1m25.113s +2.050
6 Nico Rosberg Mercedes 1m25.186s +2.123
7 Jenson Button McLaren 1m25.994s +2.931
8 Max Verstappen Toro Rosso 1m26.267s +3.204
9 Pastor Maldonado Lotus 1m28.272s +5.209

15:05 There's been much more change to the lap counts recently. Here's how that looks:

Nasr - 126
Rosberg - 106
Perez - 90
Bottas - 83
Vettel - 79
Verstappen - 68
Maldonado - 36
Ricciardo - 26
Button - 23

15:10 Vettel pits, leaving Bottas, Nasr, Ricciardo and Perez out on track.

15:17 A quiet couple of minutes here, with Nasr and Perez the only cars currently on track.

15:18 Continuing Force India's productive couple of days with its new challenger, Perez is on his 100th lap for the day.

15:23 Perez has now pitted, as Ricciardo heads back out to add to Red Bull's limited running.

15:24 Rosberg has also headed out - no soft tyre runs from the Mercedes yet today. Or super-softs at all, all winter.

15:26 And that doesn't change on this run, Nico's on the hard compound.

15:26 Based on the times we've seen in recent days, a Mercedes super-soft run would probably break the internet. So maybe it's for the best if they stick to the harder compounds for the time being.

15:34 Ricciardo - now on his 40th lap for the day - and Rosberg continue to circulate. After its compromised running this morning, we've stil only seen 26 laps from the McLaren.

15:45 Here's a look at today's headlines, as the afternoon continues to tick by:

* Bottas fastest on super-soft run
* Button and Ricciardo's days plighted by mechanical problems
* Rosberg sticks to medium and hard compound programme
* Maldonado crashes in the afternoon

15:46 @WilliamsRacing "So that's winter testing completed for us. Next stop for the guys is @ausgrandprix Well done team! #weareracing"

15:47 Third day in a row Williams has finished early. They're like the kid who completes their school test early, and naps while everyone else racks their brain about trigonometric equations.

15:48 @SauberF1Team "Felipe just finished his race simulation #FN12 #F1"

15:49 Button has just completed a run on the super-soft tyre, improving to a 1m25.327s.

15:51 His 2014 team-mate, and now McLaren's reserve driver, Kevin Magnussen is looking for ways to keep busy in 2015. The youngster was keen to tackle a certain race in France in June.

Kevin Magnussen wanted to race at Le Mans with his father in 2015

15:58 One last extra snippet from our #askKarunF1 chat with KARUN CHANDHOK. And it's about our home for the last four days, Circuit de Catalunya.

You can read the full feature here:

Chandhok answers your testing questions

@faketilke asks: "Aren't drivers tempted to NOT use the ugly final chicane, and former track instead? Seriously, are drivers fine with this chicane?"

KARUN CHANDHOK: "I find the chicane very frustrating. I never raced on the track in its previous configuration but I did some testing and it was awesome. The last corner used to be amazing.

"So yeah, the chicane, and the whole last sector, is all a bit frustrating to be honest. But we have to drive the circuits we are given – we don’t get to design them.

"I think this is a very difficult circuit. In the old days if you had a car that worked well at Barcelona you had a car that worked well everywhere. The difference is today, the way F1 teams develop, you could have Ferrari winning here a couple of years ago and then for the rest of the year Red Bull destroyed them.

"Nowadays they develop the cars so much during the season, Barcelona is no longer the benchmark that it was before. They're just adding downforce at a much higher rate than they used to in the past."

16:04 We're now an hour away from the Australian Grand Prix*!

*In terms of remaining on-track testing, not actual time.

16:05 We've got Vettel, Ricciardo and Rosberg on track. We know Bottas and Maldonado are done for the day, and that Verstappen encountered an engine problem.

16:14 Rosberg dives into the pits, with his tally on 131 laps, leaving Vettel and Ricciardo out on track.

16:20 @MercedesAMGF1 "Stunning evening @Circuitcat_eng: do we really have to go home? Much as we love our corner of the world of course!#F1"

16:23 @ToroRossoSpy "Now this is good news, Max is back! It will be good to get out for the final hour of pre-season testing #GOTOROROSSO"

16:23 Max has indeed headed out. He joins Vettel and Nasr on the circuit with 35 minutes remaining.

16:24 Here's the latest lap counts:

Nasr - 149
Rosberg - 131
Perez - 120
Vettel - 106
Bottas - 89
Verstappen - 69
Ricciardo - 58
Maldonado - 36
Button - 29

16:25 Verstappen improves to a 1m25.710s.

16:26 If you're following the action on a mobile device, the times look like this:

1 Valtteri Bottas Williams 1m23.063s
2 Sebastian Vettel Ferrari 1m23.469s +0.406
3 Felipe Nasr Sauber 1m24.023s +0.960
4 Daniel Ricciardo Red Bull 1m24.638s +1.575
5 Sergio Perez Force India 1m25.113s +2.050
6 Nico Rosberg Mercedes 1m25.186s +2.123
7 Jenson Button McLaren 1m25.327s +2.264
8 Max Verstappen Toro Rosso 1m25.710s +2.647
9 Pastor Maldonado Lotus 1m28.272s +5.209

16:33 Verstappen, on softs, improves again to 1m25.498s. Mercedes reports that Rosberg is also out on softs, albeit a scrubbed set with a focus on practice starts.

16:43 We're just about into the final 15 minutes, with Vettel, Ricciardo and Rosberg on track.

16:50 Ricciardo, Verstappen, Vettel and Rosberg have the track to themselves as we enter the final 10 minutes of testing.

16:53 Led by AUTOSPORT Editor EDD STRAW, Sauber facts may or may not have taken the internet by storm during the first test at Jerez.

As the winter programmes draw to a close, we've got one more up our sleeve, although it's not an Edd special.

Sauber driver Felipe Nasr has completed the most laps today of testing today, 159. That's about 460 miles, and the distance between London and Switzerland, where Sauber is based, as the crow flies.

16:58 We're into the final minutes.

16:58 Verstappen, Ricciardo and Perez are the cars on track.

17:01 And Formula 1 pre-season testing 2015 is done and dusted!

17:03 Here's are the day's final times:

1 Valtteri Bottas Williams 1m23.063s
2 Sebastian Vettel Ferrari 1m23.469s +0.406
3 Felipe Nasr Sauber 1m24.023s +0.960
4 Max Verstappen Toro Rosso 1m24.527s +1.464
5 Daniel Ricciardo Red Bull 1m24.638s +1.575
6 Sergio Perez Force India 1m25.113s +2.050
7 Nico Rosberg Mercedes 1m25.186s +2.123
8 Jenson Button McLaren 1m25.327s +2.264
9 Pastor Maldonado Lotus 1m28.272s +5.209

17:08 And here's the final lap tally:

Nasr - 159
Rosberg - 148
Perez - 130
Vettel - 129
Bottas - 88
Verstappen - 85
Ricciardo - 72
Maldonado - 36
Button - 30

17:18 And that's it for 2015 winter Formula 1 testing.

Thank you so much to everyone who followed the past month's action and intrigue on AUTOSPORT Live.

Here's the final report from today's session:

Bottas keeps Williams on top

There's plenty more coming up on AUTOSPORT tonight and beyond, starting with full reaction from the paddock on today's events, plus our ranking of the teams after testing.

Into the week we'll have a rundown of all the testing statistics plus our '10 things we learned' summary, GARY ANDERSON's verdict and plenty more, including our comprehensive season preview magazine on Thursday.

AUTOSPORT Live will be back for every session of the Australian Grand Prix weekend in a fortnight, and before then Race Centre Live is in action for Rally Mexico and the World Touring Car Championship season-opener from Friday afternoon this coming week.

See you then.