Thanks for joining us - we'll be back at 13:00 UK time for the qualifying session - and by the looks of things it will be very, very tight.
Free Practice 3
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Top 10: Massa, Raikkonen, Webber, Alonso, Di Resta, Sutil, Hamilton, Vergne, Rosberg
Looks as if Massa's time will be good enough for the top time...
Practice start for Alonso - he won't have time to get another lap on the board, I don't think.
1:22.069 - just lost some time in the final sector, and it consigns Grosjean to fourth.
Grosjean fastest through sector one, still quickest at sector two. Can he top the timesheets?
Vettel not quite on it - 1:22.229 gets him up to fourth. Alonso darts out for a late lap.
Looks like there'll be a flurry of quick times - all but Alonso of the leading drivers are out on track.
By comparison, Button 11th on his medium tyre run. Vergne has just gone four-tenths of a second quicker in a Toro Rosso. This is pretty wretched for McLaren.
Di Resta up to fourth, ahead of both Mercedes. Massa trumps that though - he's fastest of all by 0.006s!
Whitmarsh - "We'll change the system [for Perez] before qualifying, but it's difficult for him"
As Felipe Massa heads out, Webber improves his best to a 1:22.044, good enough for P2.
Perez's power steering is causing 'asymmetry' - there's not a lot of time to fix and correct that, with seven minutes of the session remaining. Oh dear.
Webber the latest man out on the Circuit de Catalunya. Medium tyres for him.
He can! Very quick on the final sector and his 1:21.907 is three-tenths clear of Alonso. Anyone else going to show their hand?
Raikkonen just a whisker faster than Alonso after two sectors... can he finish it off?
Raikkonen heads out. Is there a lesson that the Mercedes pair both went quicker on their third lap, after a cool-down tour, than they did on their first flying effort?
Other than that, it's quiet ion track. Decent lap from Gutierrez puts him up to ninth.
Rosberg finds another tenth of a second this time around - Perez jumps to 13th, and Hamilton improves by another tenth as well.
Rosberg and Hamilton both back off to cool the tyres ahead of another quick lap. Alonso ducks into the pits.
McLaren making little progress - Perez's first timed lap of the hour is several seconds down on the field and he had to back down at the end.
Hamilton just a tenth quicker than Rosberg. Still a big gap to Alonso, who has thrown down the gauntlet with that effort. The question will be which of Ferrari's rivals can compete with the Spaniard?
1:22.254 - an improvement of three-quarters of a second. Rosberg slots into second, six-tenths down on Alonso.
Six-tenths up at sector two. Medium tyres appear to offer a very signficant advantage....
Alonso begins a flying lap. If he gets a good run, we should be able to compare the advantage the tyres bring. 0.248 up on his best at the first sector.
Alonso and Rosberg are out on medium tyres - this should be interesting with qualifying in mind.
Hulkenberg's tyres getting too hot - his Sauber engineers tell him to reduce the temperature by 20 degrees! Easier said than done...
Signs of action here - Rosberg is out in the Mercedes. The team have not shown their true pace yet - just the long runs, which leave them low down on the timesheets.
Skies are pretty dark over Barcelona, but the rain has held off so far and is expected to stay away.
Vettel back on track and posts a lap three-tenths of a second shy of his best this session.
Plenty of work being done in the McLaren garage. What has happened to them in the last 12 months?
Looks like we've worked out what went wrong with Perez's McLaren - the turning vanes flew off as he ran over turn 16's kerb.
The gap between the leading drivers shows as much - Alonso to Webber in sixth separated by less than half a second.
I'd say any of four teams have a realistic shot at pole today - Red Bull, Ferrari, Lotus, and Mercedes.
Out on track: The Caterhams, Gutierrez and Button.
Most drivers are in the pits at the halfway stage of the session. Plenty of data to interpret, final tweaks to be made.
"I'm having a suspension with the suspension," Perez communicates. He's told to pit straight away.
Button gains a single place, and about three-tenths of a second.
"Looking at the other cars, it seems to be taking a couple of laps for the tyres to come in" - that's what Perez is being told. The race engineers are right - but that's not the cure to all McLaren's problems...
Massa slots in to fourth place, but Button is about 1.5s adrift in 10th after his first effort.
Hamilton has just come into the pits after a 13-lap run, so clear enough that the Mercedes pair were running an altogether different simulation, based on a race run.
And right on cue, Fernando Alonso rises to the top - not by much, just 0.036 of a second - but enough to excite the Spanish crowd.
Top 10 at present (some big names like Ferrari, McLaren and Red Bull yet to set meaningful times): Grosjean, Riakkkonen, Vettel, Webber, Di Resta, Vergne, Maldonado, Ricciardo, Sutil, Bottas
And sure enough Grosjean goes top, 1:23.042. The Lotus is running very, very low to the ground, but it's working very well.
As if to illustrate the point, Romain Grosjean is on an even quicker lap after two sectors...
1:23.152 - Kimi Raikkonen sets the fastest time of the session so far. The Lotus looking excellent again this weekend.
Drivers starting to get busy now - Hulkenberg, Sutil, Vergne, Maldonado and Webber amongst the men setting some times.
1:23.920 from Vettel - a clear second faster than anything else we've seen this morning. Still room to improve, though. He's on hard tyres, for a start.
Back on to the action on the track, where Sebastian Vettel is on a flying lap.
And in an amusing stunt, Fernando Alonso's Ferrari was flown into Spain by helicopter. Risky?
James Frankland has composed the ultimate guide to the Spanish GP.
Gutierrez in the Sauber has become the only other man to post a lap - his first effort was good enough for third, but his 1:25.013 has slotted him top now.
Whitmarsh sounds pretty downbeat at the moment. McLaren have yet to see that big step up in performance this weekend, and they desperately need it.
McLaren principal Martin Whitmarsh on Sky: "I can't predict when we'll be back but we'll be working hard'
Hamilton and Rosberg are clearly working on a different test with a higher fuel load - the Brit's times are coming down, but he's in the 1:27s at the moment.
Giedo van der Garde posts a 1:25.917, while Charles Pic tops the session with a 1:25.635. Caterham, get a screengrab while you can...
Now here's something you don't see every day... a Caterham 1-2 on the timesheets!
To put that in some context Vettel set a 1:22.808 yesterday - those times have a long way to come down.
First times of the day from the Mercedes - Rosberg 1:29.468, then Hamilton beats it witha 1:28.350
Have you seen our F1 video yet, with five things you need to know about the Spanish Grand Prix?
Red Bull running an aero test with some garish hi-visibility paint on the front to help engineers measure success of new parts.
Force Indias, etc... back in the pits after set-up laps.
Track temperature recorded at 21C. A million miles away from the conditions at the last race in Bahrain, but more like what the teams will know from pre-season testing.
Loud cheers for the Ferrari duo heading out. Imagine how excited the Spaniards will be when the real racing starts...
Hard tyres the order of the day on every car we've seen so far.
Away we go! Lots of cars straight out on installation laps - both Force Indias, and the Toro Rosso of Ricciardo.
It's dry in Spain at the moment - although on the radar showers are about 20km away from the track. Looks as if we'll avoid them, however.
Hello and welcome to continued live text commentary from the Spanish Grand Prix.