07:46 Welcome to AUTOSPORT's live coverage of free practice for the Spanish Grand Prix, as Formula 1 returns from a three-week break to kick off the European leg of the season.

07:48 As you can see, the sun is shining in Spain this morning, meaning the teams will get decent conditions to try out what is traditionally a busy Friday in terms of new parts appearing on the cars.

07:51 There will be a lot of attention on the Mercedes v Ferrari battle this weekend - particularly if the balance in power between the two shifts at all as a result of new parts on either car.

Ferrari's Sebastian Vettel admitted yesterday that his team's performance here will offer a key barometer for the rest of the season:

"Barcelona, historically, has always been a place where teams have brought updates to cars, sometimes bigger or smaller," he said.

"We've probably done the same as everyone else, but hopefully we'll have a bigger update and a better laptime to catch up to the guys in front, Mercedes.

"If we can show we've made a step forward here I guess that would be the case for the races coming."

07:58 It's not a traditional 'parts' upgrade, but there will also be lots of attention on the new colour scheme on the McLaren this weekend. Gone is the silver that has been the team's predominant colour since it dropped its famous Marlboro colours for the 1997 season.

08:00 The pits are open, here we go for Spanish GP FP1.

08:01 Plenty of cars out early - Maldonado, Vettel, Sainz, Verstappen, Stevens, Nasr, Palmer, Massa and Marciello - in Ericsson's Sauber.

08:03 Massa is the first (and so far only) driver to stay out for a second lap on these installation runs.

08:04 Maldonado is told to do an "aggressive burnout" out of his pit box. Sounds like fun.

08:05 As usual with the first European event of the season, aero upgrades are a common theme up and down pitlane. Among them, Red Bull has a revised nose, running on Kvyat's car.

08:06 Speaking of Red Bull, Ricciardo reports an engine problem when he applies full throttle. The team confirms it sees it on the data, and he's now back in pitlane.

Of course, power unit problems aren't a new thing...

Renault won't chase Formula 1 performance until reliability solved

08:06 Every car has appeared on track now.

08:07 Unfortunately for us, nearly all of those cars have returned to the pits without setting a time so far!

08:08 Rosberg locked up into Turn 10, took to the old part of the circuit there. Other than adding plenty of dust to his tyres, no real harm done and he starts a new lap.

08:08 Rosberg posts the first time of the session - 1m31.039s - but it's a pretty meaningless time given that lock-up.

08:09 Hamilton is next to set a lap, but his 1m31.205s is slower than Rosberg's lock-up lap.

08:09 The Mercedes drivers are the only ones on track at the moment, as nobody else seems that interested in making use (just yet) of the hard tyres that they have to give up after the first 30 minutes.

08:10 Hamilton and Rosberg pit without improving those unrepresentative 1m31s, so now we have a silent track.

08:11 @RenaultSportF1: "Barcelona is in the middle of the table for the power unit. Only 45% of the track is taken at full throttle, the lowest % of the season so far"

08:12 Stevens breaks the silence on track for Manor, and his team-mate Merhi joins him.

08:15 @Lotus_F1Team: "Now for some feedback and chat with the engineers for both drivers"

08:16 Merhi is told that his tyres are slightly below temperature. That's unlikely to be an issue too often this weekend when the temperatures rise in the sessions that count.

08:16 Stevens posts a 1m37.732s to go a distant third in the Manor.

08:17 Merhi posts a 1m38.649s, while Stevens improves by a big chunk to a 1m34.661s.

08:17 Our technical expert CRAIG SCARBOROUGH has a pic of the new Red Bull nose we mentioned earlier.

@ScarbsF1 New nose and flow viz

08:19 Susie Wolff - in action for Williams this morning - slots into third (briefly) before Maldonado bumps her down to fourth. The Lotus man splits Rosberg and Hamilton at the top.

08:19 Sainz tells Toro Rosso he has a "really bad bite point" via the team's radio.

08:20 Ferrari chief Maurizio Arrivabene is wearing an arm band with '27' on it. Gilles Villeneuve died on this day in 1982.

08:20 Hamilton and Rosberg get down to business - the world champion is first up with a 1m28.993s.

08:20 Vettel is up to second, Verstappen to third.

08:21 Rosberg's first proper lap is comfortably enough for P1 - 1m28.384s puts him six tenths clear of Hamilton.

08:21 Everyone except Fernando Alonso is on track at the moment - remember, the teams only have another eight minutes before they have to give up this first set of tyres.

08:22 "Use the outlap display for your tyre targets," Sauber tells Marciello, who is replacing Ericsson in the Sauber for FP1.

08:22 Vettel takes top spot by two tenths with a 1m28.141s.

08:22 Raikkonen is told that his tyres at 25C below temperature at the front and rear.

08:23 Current top 10:

1 Vettel
2 Rosberg
3 Hamilton
4 Verstappen
5 Maldonado
6 Nasr
7 Massa
8 Perez
9 Palmer
10 Button

08:24 Rosberg is told "cool the brakes, and then you can push again".

08:24 Perez asks how many more laps does he have on this stint. Force India reply that he "has two full laps after this one."

08:24 Hamilton re-takes top spot with a 1m27.509s - 0.6s clear of Vettel's Ferrari.

08:25 Bit of a wild moment from Marciello exiting Turn 9. Copped a bit of oversteer which pushed the Italian wide, recovered over the astro turf.

08:26 We have a Mercedes/Ferrari lockout of the top four (how often have we had that this year?). It's currently Hamilton, Vettel, Rosberg, Raikkonen.

08:26 Kvyat is told "Mode 11 and go for the lap."

Red Bull also inform him to make space as he may only have one timed lap left.

08:26 We've just had a Force India off track briefly, Perez at Turn 4. He rejoins and continues.

08:27 We've had times from 18 cars so far in the session. Only Kvyat and Ricciardo - for Red Bull - are yet to set a lap.

Sure enough, Kvyat puts his first timed effort in and he slots in ninth.

08:27 Rosberg makes it a Mercedes 1-2 at the front - 1m27.533s.

08:28 In his usual manner, Kimi informs Ferrari that he simply has no front end in his car.

08:28 We're inside the final two minutes before the first set of tyres are no longer allowed to be used. Ricciardo is back in the pits, so he won't be setting a time in this first part of FP1.

08:28 Big lock-up for Ricciardo - back on track after his earlier engine concerns - at the last chicane.

08:29 Here’s a pic of the Ferrari tribute to Villeneuve we mentioned a little earlier.

@ScuderiaFerrari Remembering Gilles #27 #GillesVilleneuve #redseason #Arrivabene #SpaGP

08:29 Rosberg is told to check the brake balance, before a "qualifying turnaround.

08:29 Wolff is given "info on the positioning" - "20cm to the left and 20cm short". Could that be feedback on a braking point from the Williams team?

08:30 Everyone makes it back to the pits within the first 30-minute window, so things go quiet.

08:31 Top 6:

1 Rosberg
2 Hamilton
3 Vettel
4 Raikkonen
5 Sainz
6 Verstappen

08:31 BEN ANDERSON is watching the cars trackside, and has spotted a couple of the early moments: "Massive moment for Marciello as the Sauber rear steps out through three. Vettel locks up massively at Turn 1 and takes to the escape road."

08:31 Toro Rosso is concerned whether Verstappen's car is bottoming out on the straights, to which he replies a little bit on the main straight.

08:32 @RenaultSportF1: "Speeds on these two straights will peak at over 300kph with DRS open, with the maximum speed being just over 325kph on the main straight."

In Mercedes-land, Hamilton has already passed through the speed trap at 335km/h.

08:33 EDD STRAW: "Drawing conclusions from performance during the first 30 minutes of FP1 is pretty much pointless, but for what it's worth, nothing in what we've seen so far suggests that Ferrari has closed the gap to Mercedes in terms of single-lap pace."

08:34 More from BEN ANDERSON at the end of this first phase of the session. It's good reading for Mercedes fans.

"We've only had half an hour of running of course - and we can't be sure of fuel loads, etc - but the Merc still looks to be the best car in the field from where I'm standing.

"It's the only car that can take a nice, tight entry in Turn 3 at speed without running out of road in the exit."

08:37 More on the speed traps, and it's only Merhi's Manor (17th fastest) that prevents an all-Renault lockout of the bottom four places in that particular chart.

08:38 EDD STRAW: "Drawing any conclusions from the first half-an-hour of FP1 is pretty much pointless. But for what it's worth, there's nothing there to suggest Ferrari has closed the gap to Mercedes in terms of single-lap pace."

08:40 Gaps at the top:

1 Rosberg
2 Hamilton +0.176s
3 Vettel +0.808s
4 Raikkonen +1.492s
5 Sainz +2.220s
6 Verstappen +2.322s
7 Nasr +2.503s
8 Massa +2.506s
9 Kvyat +2.648s
10 Marciello +2.675s

08:40 It's a nice day to be sitting in the Spanish sunshine. Which is pretty much what fans are doing at the moment, while everyone's in pitlane.

08:41 @WilliamsRacing: "@Susie_Wolff is working @ValtteriBottas' #FP1 program, so she hops out to wait for conditions to improve #SpanishGP"

08:41 EDD STRAW: "Hamilton is fastest in the speed traps so far, registering 335.6km/h in the trap located 220 metres before the first corner. The fastest non-Mercedes-powered car is Nasr's Sauber-Ferrari, in fifth place at 326.2km/h."

08:45 Still nothing happening on track, TV directors keeping busy with shots of reflective motor home exteriors, and drivers chatting.

08:47 Felipe Massa is currently eighth. While we've got a couple of minutes, why not have a read of LAWRENCE BARRETTO'S latest column, on his second-coming with Williams?

The Massa story isn't over yet

08:47 EDD STRAW: "The idea of making the first set of tyres used in FP1 usable only in the first half-hour is to avoid the dead track time early on. The trouble is, as we see here, that often leads to not much happening for a while after the first 30 minutes has ended."

08:48 The silence is broken by Will Stevens heading out in his Manor.

08:49 Here's a look at the new colours of the McLaren on track:

From trackside, BEN ANDERSON says "it's quite striking. A definite improvement with those orange flashes."

08:50 Merhi is told by Marussia to do a practice start at the end of the pitlane, along with a bite point test.

08:50 Alonso and Hulkenberg join the Manor drivers on track, as more teams start getting ready to send their cars back out.

08:52 "DRS on the start finish straight only," McLaren tells Alonso.

08:52 Alonso looks comfortably on course for an improvement from P15 here.

08:52 BEN ANDERSON kept busy trackside by putting together this little explanation for the dead air.

"I suspect a combination of factors for the lack of action in this session so far.

"Teams obviously know this track like the back of their respective hands, so they don't need to pound around relentlessly.

"Most will want to do some live analysis of upgrades too. But there is a concern over the engine mileage for many, now that they are limited to four per car for the season.

"Part of the push to go back to five is related to the need to allow the cars to run more laps on Friday."

08:52 Sure enough the McLaren goes seventh with a 1m29.813s.

08:54 Hulkenberg goes sixth with a 1m29.623s. Remember, everyone is having to rejoin the action on a new set of hard tyres after giving up that first set from the first 30 minutes. Track temperature hasn't changed much since the start of the session, so it's only really the new rubber that can be making a difference at this stage.

08:55 Another improvement for Hulkenberg - he's up to fifth behind the Mercedes and Ferrari drivers.

08:55 Toro Rosso reminds Verstappen not to weave in the pitlane.

08:57 Fancy slow-mo of Button pounding over the final chicane's kerbs in the reliveried McLaren. He's 15th.

08:57 Mercedes tells Rosberg there's a 12s gap behind Sainz, which is a good space to get a lap in.

08:58 BEN ANDERSON: Big lockup for Merhi and he's across the escape road at Turn 1.

08:58 Despite the blazing sunshine over the circuit, plenty of drivers are getting radio messages telling them that tyre or brake temperatures are slightly low. It's probably just that they're not working the car too hard on their outlaps because they expect it's hotter than it is.

08:59 Hamilton sets a new fastest lap of the session - 1m26.898s. Rosberg slots in with a 1m27.043s just a few seconds later.

We've had a 1m27.846s from Vettel to stay third in the Ferrari.

08:59 Force India reckons Alonso found 0.9s on his first lap of this run, and passes that information on to Perez via the team radio.

08:59 The Toro Rossos are maintaining their position towards the sharp end - both Sainz and Verstappen have improved to get ahead of Raikkonen, who is on an outlap.

09:00 The McLaren is "very oversteery," according to Jenson Buttton.

09:00 Here's the top 10 with 30min to go:

1 Hamilton
2 Rosberg
3 Vettel
4 Sainz
5 Verstappen
6 Raikkonen
7 Hulkenberg
8 Alonso
9 Nasr
10 Massa

09:01 Vettel improves again on his next timed lap, but he only finds 0.040s so he won't be troubling the Mercedes drivers just yet.

09:01 The Mercedes airwaves are full of advice for Hamilton on his diff settings to correct his understeer problem.

09:02 As expected, Raikkonen's first lap of this run gets him back ahead of the Toro Rossos, and just a few hundredths behind Vettel.

09:02 Marciello is one of three FP1 test drivers. He’s 13th, Palmer in the Lotus is 15th and Wolff 17th in the Williams. The Italian even had time to catch up with Marcus Ericsson, and reassure him he’s looking after the Sauber C34.

@SauberF1Team Marcus will take over from #FP2 on #ME9 #F1 #SpanishGP

09:02 Button really isn't happy with his McLaren. "There really has been a shift in balance," he says, after complaining of oversteer earlier.

09:03 Gaps at the top:

1 Hamilton
2 Rosberg +0.145s
3 Vettel +0.908s
4 Raikkonen +0.934s
5 Sainz +1.304s

09:03 Rosberg moves clear of Hamilton at the top with a 1m26.828s, so he's ahead by 0.070s.

09:03 Still only two laps - none of them timed - for Ricciardo as Red Bull continues to investigate problems with its Renault power unit. Team-mate Kvyat is seventh with the newly-nosed RB11.

09:04 Button is also talking about the Honda powerplant in his McLaren. "We didnt get the power we expected," referring to the start finish straight.

He added that the power arrived "very late."

09:05 A couple of little moments for Hamilton - one some exit opposite lock, the other a slight lockup into Turn 10.

09:05 Rosberg is asked to cool the front left, as it is a "little hot."

09:06 Rosberg is on course to improve again - seemingly by a couple of tenths - but he aborts the lap with a big slide out of the final chicane before heading for the pits.

Interestingly, the Mercedes went the wrong side of the bollard at the pit entry.

09:07 Verstappen informs Toro Rosso that he got held up by Raikkonen, who had some oversteer in Turn 12.

09:07 Only Verstappen, Perez and Raikkonen on track - and things get even quieter as Perez comes in too.

09:08 BEN ANDERSON has an update on Verstappen's team-mate, and one of Toro Rosso's former drivers.

"Sainz really hanging on to the STR through Turns 2 and 3, lots of corrections.

"The Red Bull of Kvyat by contrast looks super smooth."

09:08 Raikkonen complains that the seat is getting very hot in his car. That must be uncomfortable for the Finn.

09:08 Raikkonen and Alonso have the track to themselves at the moment, with just over 20 minutes to go in FP1.

09:08 LAWRENCE BARRETTO: "The grandstand on the outside of Turn 9 may be empty, but it's covered from top to bottom in banners and flags for one man - Fernando Alonso. One reads in Spanish: 'Fernando, we are always with you'. The Spaniard has completed 17 laps so far, only Lewis Hamilton has done more."

09:10 Here's another snap of the new Red Bull front wing, and some aero paint sticking to Kvyat's front tyres.

09:10 Rosberg is under investigation for missing the bollard at the pit entry just a few minutes ago.

09:13 Wolff sets her fastest time of the session so far in the Williams. She's currently 17th on a 1m30.543s, 0.3s behind fellow reserve driver Jolyon Palmer in the Lotus.

09:13 Massa improves in the other Williams - he's currently eighth and two seconds off the pace.

A few oversteer moments late in the lap for the Brazilian, initially through the chicane, then in the final corner itself.

09:14 Another improvement for Wolff - she's up to 10th with her latest effort.

09:15 Top 10 with 15 to go:

1 Rosberg
2 Hamilton
3 Vettel
4 Raikkonen
5 Sainz
6 Verstappen
7 Kvyat
8 Massa
9 Hulkenberg
10 Wolff

09:16 Gerhard Berger and Christian Horner are having a chat on pitwall. All looks pretty chilled, particularly Horner given the power unit dramas that have marred Ricciardo's session.

09:17 At the bottom of the order, we still have Ricciardo as the only driver not to set a time - having only managed two laps in this session.

09:17 Nasr moves into the top 10 - a 1m29.140s puts him ninth in the Sauber.

09:18 Rosberg tops the lap count in this session with 20. Hamilton and Alonso are next up on 19, with Sainz following on 18.

At the other end, Kvyat and Maldonado are the only non-Australians still in single figures.

09:19 Here's another shot of the new-look McLaren. What do you think? Let us know on Twitter with the hashtag #autosportf1

09:19 As the track gets busy again, we're seeing quite a few 'green' sector times, which means improvements are on the way.

09:20 Rosberg complains of a "very poor start" on the Mercedes team radio. He'll be hoping that's not the case on Sunday.

09:20 Marciello and Palmer - reserves on duty at Sauber and Lotus, slot into 11th and 12th.

09:21 Marciello is pushing hard. He got some air over the kerbs at the final chicane and on the following lap went straight on at Turn 10, using the old circuit.

09:21 Eight minutes to go and Ricciardo re-appears.

09:22 So far on this run, the Mercedes are lapping in the 1m31s and 1m32s - some way short of the 1m26s laps we saw from the Silver Arrows earlier in the session.

09:23 Vettel's first sector is up on Rosberg.

09:23 "The track position is bad," says Vettel, trying to find some space with only a few minutes remaining in the session.

09:24 Vettel loses a bit of time in the middle sector.

09:24 LAWRENCE BARRETTO: "Jolyon Palmer is doing a solid job in his third successive FP1 outing at Lotus. The Briton is currently 12th quickest, 2.848s off the pace but four tenths clear of team-mate Pastor Maldonado."

09:24 The Ferrari then loses a lot of time in the tricky final sector, so he finishes the lap 1.4s down and doesn't even improve. His lap fell away by around 1.2s in the final sector alone.

09:25 Ricciardo's first timed lap moves him up to P16 in the Red Bull. He's a tenth behind Button, who according to the Red Bull team on the radio (when it was informing Ricciardo about what he was aiming at), set that lap on low fuel.

09:25 Marciello is told to make sure the tyre temperature doesn't drop below the target on his next lap.

09:26 Vettel pits after that lap that looked so promising until he lost so much time in the final sector.

09:27 With three minutes remaining, the only drivers in pitlane are Kvyat, Nasr, Hulkenberg, Marciello and Maldonado.

09:27 Mercedes says on Twitter that Hamilton is "not 100 per cent happy with the setup currently. Work to do in the break..."

09:28 Ricciardo, meanwhile, has improved to 11th.

09:28 LAWRENCE BARRETTO: "Susie Wolff, driving in the first of two planned FP1 planned appearances this season, is currently 14th, five tenths off Williams team-mate Felipe Massa having completed 22 laps."

09:29 Jenson Button reports over the radio to McLaren that "the balance is completely wrong with this wing".

09:30 Raikkonen is furious on the Ferrari team radio. "What are we doing, we go out, straight into traffic?"

09:31 Ricciardo slips into the top 10, going ninth at the end.

09:32 Alonso has executed a neat little 360-degree spin at Turn 12. Points for style, none for time.

09:33 That's the last real action of a fairly quiet FP1 session in Barcelona.

09:33 LAWRENCE BARRETTO: "Nico Rosberg's leading time is two tenths quicker than his Mercedes team-mate Lewis Hamilton managed when the reigning world champion topped the times in this session last year."

09:34 Rosberg finishes the session on top, just 0.070s ahead of Hamilton, but a comfortable 0.978s clear of Vettel's Ferrari in third.

09:34 Here's how the order looks:
1. Rosberg
2. Hamilton
3. Vettel
4. Raikkonen
5. Sainz
6. Verstappen
7. Kvyat
8. Massa
9. Ricciardo
10. Nasr

09:35 And the bottom half:
11. Hulkenberg
12. Marciello
13. Palmer
14. Wolff
15. Alonso
16. Button
17. Perez
18. Maldonado
19. Stevens
20. Merhi

09:37 The second session will, of course, see Marciello, Palmer and Wolff replaced by Ericsson, Grosjean and Bottas, respectively.

09:40 Another strong start for Mercedes, here's the full report. We'll see you again at 1pm BST for the second session.

Spanish Grand Prix FP1: Nico Rosberg leads Lewis Hamilton

11:51 Welcome back to AUTOSPORT Live's coverage of the Spanish Formula 1 Grand Prix.

11:51 We're about 10 minutes away from FP2, nice work if you've timed your Friday lunchbreak accordingly.

11:52 Mercedes topped the times this morning and finished FP1 nearly a second clear of the best of the rest, Sebastian Vettel's Ferrari.

Our full report is three entries below.

11:52 Lotus confirmed between the sessions that Pastor Maldonado's restricted running earlier today was thanks to a "minor" gearbox glitch. He is expected out for this session.

11:54 Nico Rosberg led the way, but he did earn the ire of the stewards for entering pitlane after the designated 'entry' cone.

Nico Rosberg given reprimand for F1 practice pit entry incident

11:56 In other news to catch-up on before we get underway, Valtteri Bottas' manager Didier Coton has vowed to explore "all the different possibilities" for the Williams driver's long-term future in Formula 1.

Manager Didier Coton keeping Valtteri Bottas' F1 options open

11:56 And Formula 1's Strategy Group will next week reject a proposal to increase the engine allocation for this season to five, AUTOSPORT has learned.

F1 Strategy Group to vote against proposal for a fifth engine

12:00 Here we go, the pits are open and FP2 is underway.

12:00 And the first driver out of the pits at the start of the session is Sauber's Ericsson, who does a practice start and takes to the track.

12:01 Each driver has one set of the hard-compound Pirellis and one set of the mediums for this 90-minute session. The usual strategy is to do some running on the hards, then bolt on the mediums and do a performance run, then do some long runs on either or sometimes both tyres.

12:02 Ericsson embarks on the second lap of his run.

12:03 Ericsson said on his outlap that "something was wrong with the clutch setting". Sauber says it will come back to it "after the run".

12:03 And Ericsson sets the first time of the session - a 1m33.041s.

12:04 Force India tells Sergio Perez that the wind is pretty much the same as the previous session.

12:04 Remember, that's Ericsson's first flier of the day as he sat out FP1 to allow Marciello some running.

12:04 Track temperature is at 46C now - that's over double what it was for much of the first session.

12:06 Vettel is the first of the big guns to head out on track. We've now got half-a-dozen cars out there.

12:06 And now Raikkonen joins him.

12:07 Merhi sets hits first flier - a 1m40.517s to go second.

12:07 There's an engine change going on at Red Bull - our snappers at LAT Photographic are down in front of Daniel Ricciardo's car:

12:07 Ericsson improves his fastest time to 1m32.803s to consolidate what will be a short-lived stint at the top of the timesheets.

12:08 And Vettel goes fastest on a 1m29.394s

12:08 There's work going on down at Lotus as well, on Pastor Maldonado's car. He had a gearbox problem in the first session.

12:09 Grosjean sets his first time, a 1m33.016s to go third behind Vettel and Ericsson.

12:09 Decent snap of turn-in oversteer at Turn 10 for Grosjean, Palmer was in that car in FP1.

12:09 Rosberg is told that he has a four-second gap behind him to Perez, as he tries to find space for a lap.

12:09 We also have Rosberg and Hamilton on track for Mercedes.

12:10 Rosberg is on a flier - looks set to go fastest although he still has two-thirds of the lap to complete.

12:11 Rosberg goes second fastest on a 1m30.624s.

12:11 Vettel improves his fastest time to a 1m29.085s. He's now 1.354s ahead of new second-place man Sainz, with Rosberg in third. We will see much faster times as the session progresses though.

12:12 "I have no grip whatsoever, so I don't know what's happened," says a grumpy-sounding Raikkonen.

12:12 We now have 17 cars on track, so it's got very busy out there. Button has just gone eighth on a 1m31.136s.

12:12 Vettel returns to the pits after a five-lap run.

12:13 Rosberg goes fastest on a 1m29.075s, just 0.010s quicker than Vettel.

12:13 Perez is asking "what is my pace right now?". His best lap so far is a 1m32.007s, so he's only 11th fastest out of 15 so far.

12:13 Verstappen up to third on a 1m29.675s. But he is complaining of understeer.

12:14 Alonso puts a McLaren into fourth place on a 1m29.803s .

12:14 But Raikkonen goes third and immediately relegated his old team-mate to fifth.

12:14 Rosberg is told that the "wind is similar", (to FP1, we guess), and he is again told of the gap he has around him in terms of clear air.

12:14 Hamilton on a flier...

12:14 ...and goes fastest on a 1m27.826s.

12:15 After 15 minutes, the order is:

1 Hamilton, 1m27.826s
2 Rosberg, 1m29.075s
3 Vettel, 1m29.085s
4 Raikkonen, 1m28.108s
5 Verstappen, 1m29.518ss
6 Alonso, 1m29.803s

12:15 Replays show Bottas running pretty wide at Turn 9, with the tailwind there no doubt playing its part.

12:16 Someone has lost something on the front straight. Serious debris. Red flag.

12:16 A big chunk of bodywork has come off the engine cover of Grosjean's Lotus. Pieces of black and gold all over the front straight.

12:17 "No grip whatsoever, it feels very different the car now," - more misery from Raikkonen.

Ferrari says it wants to see what the balance is like on the softer tyre in this session.

12:17 "I lost something in a straight line," explains Grosjean.

12:18 The Lotus' are running 'Mad Max' branding on their sidepods. Not sure what Max Verstappen thinks of this red flag.

12:18 So, with the session stopped, here's the times. All of these are set on hard-compound Pirelli tyres:

1 Hamilton, 1m27.826s
2 Rosberg, 1m29.075s
3 Vettel, 1m29.085s
4 Raikkonen, 1m29.108s
5 Verstappen, 1m29.518ss
6 Alonso, 1m29.803s
7 Sainz, 1m30.030s
8 Massa, 1m30.262s
9 Grosjean, 1m30.489s
10 Nasr, 1m30.540s

12:19 The session is back underway

12:19 Rosberg radio: "Something doesn't feel right at the moment, high speed and low speed. Late entry in some places like Turn 10, massive oversteer all of a sudden."

12:20 Bottas is the first to head back out in the Williams. He's currently 12th.

12:20 We've still yet to see anyone on the medium Pirellis.

12:20 "I cannot understand how it can be so difficult," Raikkonen adds to his earlier message. "Front and rear, it's very poor."

He's reassured that everyone seems to be struggling.

12:21 Our tech expert CRAIG SCARBOROUGH grabbed a pic of the Lotus as it returned to pitlane.

@ScarbsF1 Ouch!

12:21 And the other Williams of Massa is out too. He's on hards as well.

12:21 Williams tells Bottas the plan: "Two-timed laps pushing on both, and we're going to look at the temperature rise."

12:22 Bottas sets a personal best in the middle sector, could be on for an improvement...

12:22 LAWRENCE BARRETTO: "Speaking in the break between sessions, Susie Wolff said she made a mistake at Turn 3 on her quickest lap and lost around three tenths. She ended the session 0.845s adrift of Williams team-mate Felipe Massa. She'll be back in the car at the post-Austria GP test and then British GP first practice."

12:23 ...and he does, finding around three-tenths to go 10th on a 1m30.492s

12:23 We've now got Kvyat and Maldonado on track for the first time.

12:24 Still a relatively quiet track though - just Massa, Bottas, Kvyat and Maldonado out there.

12:25 "We still need more tyre temperature please, Dany," is the message from Red Bull on the radio.

12:25 Kvyat completes the lap to set his first 'flier' of the session - a 1m36.680s. Not a proper quick lap though.

12:25 And Vettel is the first to head out on medium-compound Pirellis.

12:27 Vettel fastest in sector one...

12:27 "Try to focus on learning all gears Kimi, focus on eighth gear in particular."

12:27 Vettel fastest in sector 2...

12:28 And Vettel goes to the top of the times with a 1m27.260s. That's 1.8s faster than his pace on the hards earlier in the session.

12:28 We've also got Ericsson on mediums now.

12:28 Vettel complains of "a lot of vibrations" on his current set of tyres, when exceeding 270km/h.

12:29 Raikkonen has joined the medium-rubber party. Let's see what he can do.

12:29 Kvyat is now up to fifth place and on course to improve again.

12:30 Kvyat goes fourth on a 1m28.736s - but he's still on the slower hard Pirellis.

12:30 In full gear, Hamilton is chilling out, sitting in what looks like a square yet comfortable chair in the Mercedes garage.

12:30 Ericsson goes sixth on his first medium-compound flier.

12:31 Raikkonen goes third fastest, 0.775s slower than Vettel, on his first flier on mediums.

12:31 Massa now heads out on mediums.

12:31 Bit of a snap for Nasr on the Turn 9 exit kerb. He then runs wide into the late chicane.

12:33 Massa is on for an improvement, let's see where he ends up...

12:34 Vettel is discussing engine maps on the radio, trying to improve driveability based on what he felt on his third lap on these tyres.

12:34 Massa goes fourth, 1.452s slower than Vettel. That's not particularly quick, but Williams always run heavy on fuel on Fridays, even on a performance run.

12:35 Rosberg heads out on mediums. Come back in about three minutes and he should be fastest...

12:35 So, currently we have the two Ferraris first and second. But both have had their quick runs on mediums. We've yet to see what Mercedes can do.

12:36 Rosberg is going for a couple of warm-up laps on his mediums, so it will be next time round that he's likely to set a quick time.

12:36 Raikkonen managed to improve on his second flier, so he's now 0.520s off Vettel.

12:37 Verstappen goes fourth fastest on the mediums on a 1m28.017s.

12:37 Rosberg is winding it up - fastest of all in sector 1...

12:37 "Can we do a lap or not?!" Raikkonen barked on the radio before that lap. He's since been asking for more information on turbo speed, which Ferrari quickly got back to him with.

12:37 Hamilton heads out on mediums.

12:38 Rosberg sets a personal best in sector 2, although slower than Vettel's outright best...

12:38 Surprisingly, Rosberg misses out on top spot that lap, setting a time 0.356s slower than Vettel.

12:39 Bottas jumps up to sixth on a 1m28.525s.

12:39 Current standings:

1 Vettel, 1m27.260s
2 Rosberg, 1m27.616s
3 Raikkonen, 1m27.780s
4 Hamilton, 1m27.826s
5 Verstappen, 1m28.017s
6 Bottas, 1m28.525s

12:40 Hamilton goes fastest of all in sector 1.

12:40 Hamilton fastest of all in sector 2...new fastest time likely coming up.

12:40 Hamilton goes fastest on a 1m26.852s.

12:40 Rosberg reports that he's getting "rejected downshifts" into Turn 1.

12:41 Rosberg is getting "rejected downshifts" in his Mercedes, and let's the team know on the radio.

12:41 Unusually, that fastest lap by Hamilton is still a few hundredths off the fastest time set this morning by Rosberg. The far higher track temperatures - it's now up to 50C - is very likely compromising grip.

12:42 We've yet to see Kvyat, Alonso, Maldonado, Grosjean, Button, Perez and Ricciardo out on mediums. Of course, we've yet to see Ricciardo go out at all.

12:42 @Lotus_F1Team Still working on Romain's car, we'll give an update on his next run shortly #FP2

12:42 Hamilton and Rosberg are now both back in the pits, leaving only Bottas and Sainz on the circuit.

12:42 Still no sign of Ricciardo this session, as Red Bull completes a power unit change.

12:44 So, as it stands:

1 Hamilton, 1m26.852s
2 Vettel, 1m27.260s
3 Rosberg, 1m27.616s
4 Raikkonen, 1m27.780s
5 Verstappen, 1m28.017s
6 Bottas, 1m28.525s
7 Sainz, 1m28.674s
8 Massa, 1m28.712s
9 Kvyat, 1m28.736s
10 Nasr, 1m29.333s

12:45 Still a very quiet track, with just Maldonado and Perez now circulating. They've recently headed out. Both are on fresh mediums, so should improve on their currently lowly positions of 14th and 17th respectively.

12:46 Alonso heads out on mediums.

12:47 Perez improves to 13th place on a 1m29.707s.

12:47 Another spot from our tech guru CRAIG SCARBOROUGH. We’ll have a full feature on the Spanish GP tech updates over the weekend.

@ScarbsF1 Leading edge of the STR splitter broken up into 3 vanes

12:48 As Perez completes that lap, he's told tyres are "just on target."

12:48 Alonso sets personal bests in sectors 1 and 2

12:49 And Alonso improves to ninth place on a 1m28.723s. That's 1.1s faster than his hard-tyre pace.

12:50 We're still waiting for Kvyat, Nasr and Hulkenberg to set times on mediums - ignoring Grosjean and Ricciardo, who have not done so but are both in the garage with problems.

12:52 We're getting into the period of the session when the serious long-run hard work is done. Hamilton, Vettel and Rosberg are all out now, the two Mercedes drivers on mediums, Vettel on hards.

12:52 "Maybe you have a virus in your computer because it's not charging anything," Fernando Alonso offering to become McLaren's new IT man.

He told the team that he wasn't noticing any charging, McLaren said it could see on the data that the batteries were harvesting energy.

12:54 Meanwhile, team-mate Button has just pitted for a front wing change. He's trying a new spec.

12:54 Kvyat is now out on the mediums. He's down in 11th place so expect him to improve. Encouragingly for McLaren, Button is now up in sixth place.

12:55 Hamilton felt like his Mercedes "under performed" on his practice start.

His team-mate Nico Rosberg also had trouble with his practice start in FP1.

12:55 Kvyat jumps up to fifth place overall, 1,1s off Hamilton's fastest time.

12:56 Replays show Vettel passing Massa on the inside - i.e. between pitwall and garages - in pitlane as the Williams driver warms his tyres.

12:57 "I've got a big vibration around third gear, when downshifting," Button reports, asking McLaren to take a look.

12:57 Hamilton is the latest driver to be warned about the car bottoming out on the main straight and into Turn 1.

12:58 Hamilton is lapping in the 1m31s at the moment.

12:59 Rosberg is in the same bracket as Hamilton pace wise, about five seconds off the performance-run pace.

12:59 "My god. This is so slow. Just no grip at all," Hulkenberg tells Force India.

If you missed the news yesterday, Hulkenberg and Perez will have to wait a bit longer yet for the updated Force India...

Force India's B-spec 2015 F1 car delayed to British Grand Prix

13:00 We have now see all drivers on mediums except for Grosjean and Ricciardo, who have both hit trouble.

13:00 For three of the four Bulls, anyway. Still no sign of Ricciardo.

@RenaultSportF1 Coming into the last 30mins and more work on race balance. Traction out of last turn is important to give overtaking possibilities

13:01 Hamilton happily circulating in the mid-1m31s bracket. Rosberg is lapping fractionally quicker, in the low 1m31s and high 1m30s. Both are on mediums.

13:02 Vettel, on the hards, is in the low 1m32s

13:02 "Wind information. Wind is dying, more direct tailwind into Turn 10," a very enthusiastic-sounding weather update from Mercedes to Nico Rosberg.

13:03 "I'm quite happy with the front wing, maybe you could go a quarter up," says an apparently happy Sebastian Vettel.

13:04 Will Stevens and Roberto Merhi are currently 18th and 19th. But don't look for them to be running at Circuit de Catalunya next week, in breaking news that Manor will skip the test.

Manor team decides to miss post-Spanish GP test at Barcelona

13:04 Ferrari has split its long runs, with Vettel on the hards and Raikkonen on the mediums. Raikkonen currently in the high 1m32s.

13:04 Vettel is also told that his front brakes are hot, and that he should try and cool them down.

13:05 Toro Rosso is also splitting its long runs. Verstappen is on hards, currently in the high 1m33s and Sainz is on the mediums, curently in the high 1m32s.

13:05 @ScuderiaFerrari Long run starting for our drivers #Seb5 #Kimi7 #redseason #SpaGP

13:06 Force India reckon they are quicker than Sauber on the hard tyre, Hulkenberg is told over the radio:

"Pace-wise we are similar to Sauber on the medium, but quicker than them on the hard."

13:08 At Mercedes, Hamilton has just dropped to a 1m33.620s - not particularly fast. Rosberg, also long-running on the mediums, did a 1m31.727s.

13:08 Looks like Hamilton has now backed right off.

13:09 Raikkonen returns to the pits, but Vettel is still out there in the other Ferrari on hard tyres. He's in the high 1m32s now.

13:09 Hamilton heads back into the pits. Rosberg is still out there, but he backed off significantly on his last lap.

13:10 In an uncharacteristic fit of rage - we assume - Ricciardo is now tearing the Red Bull garage down. Or at least accidentally knocking over some garage walling.

13:11 Meanwhile, it appears Grosjean's Lotus will be back out shortly, with industrial-strength tape supporting the engine cover after the earlier fastener problems.

13:11 Rosberg is back up to speed after his slow lap. Into the mid-1m32s again. Interestingly, Vettel is only fractionally slower on the hards, which is encouraging for Ferrari.

13:12 Grosjean has returned to the track after his earlier bodywork dramas. He's on the mediums, so expect him to bang in a time that puts him somewhere in the vicinity of 10th shortly.

13:13 Hulkenberg asks: "When are you going to get me in?"

The German driver is clearly very unhappy in the cockpit of the Force India.

13:13 Grosjean sets personal bests in sectors one and two.

13:14 And Grosjean improves to 12th fastest.

13:14 Six more laps for Rosberg, Mercedes confirms over the team radio.

13:15 Sauber explain to Ericsson that they know the track temperatures are making his running difficult, to which the Swede replies "the rears are overheating."

13:15 Rosberg is still in the mid-1m32s on his long-run on mediums. Raikkonen has now switched back to the hards to see how they go. Vettel is doing a decent stint on the hards, still lapping in the mid-1m32s

13:16 Looks like the mid-pack will be pretty close on race pace. We've got a clump of drivers all circulating on mediums on long-runs in the 1m33s - McLaren, Toro Rosso and Williams.

13:17 Replays show Bottas getting very Scandinavian through the chicane complex.

13:18 What's really holding back the McLaren-Honda partnership in 2015? Our technical expert - former F1 designer GARY ANDERSON - believes it shouldn't just be Honda taking the blame, as he answers your questions in the latest 'Ask Gary Anderson' column, which is now live.

Also look out for his thoughts on how good the Jordan 191 was, how drivers gain an edge on a track they know as well as Barcelona, Ferrari's chances of closing the gap to Mercedes this weekend, and how modern F1 compares to when he got involved in the 1970s.

Ask Gary Anderson: What's holding McLaren-Honda back?

13:19 Hamilton and Rosberg both return to the track.

13:20 Vettel asks for an update on his pace, as his engineer runs through Raikkonen and Rosberg's lap times.

13:21 Guess which driver said this?

"Do you really want to keep going and do laps and laps? Because I'm getting nothing out of it, you're just putting laps on the engine."

K.Raikkonen.
Ferrari reports back that it's still working through some test items.

13:21 Noise in the Red Bull garage. Ricciardo is strapped in and it looks like he'll get out in time for the final minutes.

13:21 All of the top four on the timesheets - Hamilton, Vettel, Rosberg and Raikkonen - are out on hards now. Kvyat, in fifth, is on mediums.

13:22 A reminder of the positions:

1 Hamilton, 1m26.852s
2 Vettel, 1m27.260s
3 Rosberg, 1m27.616s
4 Raikkonen, 1m27.780s
5 Kvyat, 1m27.943s
6 Verstappen, 1m28.017s
7 Button, 1m28.494s
8 Bottas, 1m28.525s
9 Sainz, 1m28.674s
10 Massa, 1m28.712s
11 Alonso, 1m28.723s
12 Grosjean, 1m29.086s

13:23 The most laps completed so far in this session is 34 by Bottas.

13:23 "The rear was weak at the start and it's getting weaker," says Button, although he adds: "It's diffiuclt to understand because it feels like it's coming back to me a bit."

Confusing times in the McLaren cockpit.

13:24 Ricciardo gets on track, with a tick over five minutes remaining.

13:24 Rosberg is setting a decent pace on the hards - just set a 1m30.989s.

13:26 A fun fact from Pirelli as we near the end of the session.

@pirellisport Qualifying simulations are particularly important @Circuitcat_eng. 11 out of the last 13 races have been won from pole. #SpainGP #F1

13:26 Let's see what Riccairdo can do. He's on the mediums.

13:26 McLaren asks Alonso how are his tyres, to which he responds: "Good. Consistent."

Not too many drivers have reacted to a question about tyres in this session with a positive answer.

13:27 Ricciardo set a pretty decent pace in sector 1, but backed off in the middle sector.

13:28 Just ahead of Ricciardo - and possibly a factor - Grosjean ran wide exiting Turn 10 and brought plenty of dirt onto the road.

13:29 Ricciardo goes 13th, 2.246s off the pace.

13:29 Grosjean states something "big" happened with the rear of the car after that wiggle at Turn 10.

13:30 The chequered flag is out, drivers will finish these laps then head to the pits.

13:31 A little earlier, Stevens ran wide and took his Manor off-road at Turn 5. Rejoined and is back in the garage.

13:32 A discussion on the Red Bull radio reveals that Kvyat was expected to do another lap, but missed the finish line by 2s at the end of the session.

13:33 Here's the final times:

1 Hamilton, 1m28.852s
2 Vettel, 1m27.260s
3 Rosberg, 1m27.616s
4 Raikkonen, 1m27.780s
5 Kvyat, 1m27.943s
6 Verstappen, 1m28.017s
7 Button, 1m28.494s
8 Bottas, 1m28.525s
9 Sainz, 1m28.674s
10 Massa, 1m28.712s
11 Alonso, 1m28.723s
12 Grosjean, 1m29.086s
13 Ricciardo, 1m29.098s
14 Maldonado, 1m29.217s
15 Nasr, 1m29.333s
16 Ericsson, 1m29.361s
17 Hulkenberg, 1m29.601s
18 Perez, 1m29.707s
19 Stevens, 1m31.929s
20 Merhi, 1m32.751s

13:37 So one session apiece for the two Mercedes drivers. Rosberg by 0.070s in FP1 over Hamilton, and Hamilton by 0.408s over Vettel in FP2.

13:38 A relatively quiet day, just the one red flag - in FP2 when the engine cover on Grosjean's Lotus decided 100 parts was better than 1.

13:39 Red Bull endured more Renault problems, with Ricciardo limited to a handful of laps in each session. He was 13th in FP2, having only appeared in the final minutes.

But they can take heart from Kvyat (fifth), Verstappen (sixth) and Sainz (ninth) all finishing inside the top 10 with power units from the French manufacturer.

13:42 Here's the full session report:

Lewis Hamilton fastest from Sebastian Vettel

13:43 That just about wraps us up for today, thanks for tuning in. Stay tuned to AUTOSPORT.com today for more news, reaction and analysis.

13:43 We'll be back tomorrow morning from 10:00 BST for FP3, before Spanish GP qualifying at 13:00 BST.