14:02 All the cars got away for the formation lap. They are now lining up on the grid again ready for the start. Hamilton keen to slow the pace at the end of the formation lap to bunch the field.

14:01 Riku says: "Paul Hembry of Pirelli has informed that they have provided a new set for Kimi for the race, so he does have a new set of options that are just fine." Thanks for the update!

14:00 The engineers clear the grid, we are ready for the formation lap.

13:58 The mediums are expected to be the tyre of choice, with most drivers planning to limit their time on the slower hard tyres.

13:56 Of the top ten, Rosberg, Hamilton, Vettel and Raikkonen were the only drivers to save a set of mediums for the race. But my understanding is the saved tyres for Raikkonen are the ones Ferrari overcooked in the blankets.

13:55 Grosjean, Maldonado, Hulkenberg, Perez, Stevens and Mehri start on new mediums. All the others are on used mediums.

13:53 The grid is starting to clear of all the hangers on. Just drivers, cars and engineers left now.

13:51 The weather is beautiful at the Circuit de Catalunya and track temperature is up to 44C, which is 1C lower than yesterday.

13:49 Other cars to keep an eye on are the two Red Bulls, which were not happy to qualify so far down the grid. Beating Toro Rosso is a must for them this weekend as speculation continues to grow over the future of the team.

13:43 Lots of focus on the two McLaren drivers too. Can they score their first points this year. Alonso was optimistic yesterday, Button less so.

© Sutton Images

13:40 Of course, Raikkonen has a whole different set of problems starting behind two Toro Rossos in seventh place. He will need to think outside the usual pit strategy to work his way forward.

13:35 Ferrari are hoping to be more competitive on race pace than they were in qualifying and the ace up their sleeve might be tyre management. The talk in the paddock ahead of this race is of the choice between a two- and three-stop strategy. If Ferrari can make a three-stop work by maintaining a decent pace they could challenge Mercedes. A long shot, but something for both teams' pit walls to think about.

13:32 The cars are heading to the grid as I type. They have the chance to do a few sighter laps before the pit lane closes in 15 minutes.

13:30 Welcome to live coverage of the Spanish Grand Prix. The big question today: Can Nico Rosberg convert his first pole position of the season into his first victory of 2015.

Lap 1

Hamilton gets a poor start and falls behind Vettel. Rosberg gets away well to hold the lead.

Bottas remains fourth as Verstappen passes team-mate Sainz to get up to fifth.

Lap 2

Raikkonen is already up to fifth ahead of both Toro Rossos. Rosberg leads by 1.1s at the front.

Hamilton made a very slow start and was lucky not to lose a place to Bottas too. He is now 1.2s behind Vettel.

Massa is attacking Sainz and should have a good straight-line speed advantage.

Lap 3

Massa gets the job done and passes Sainz for seventh into the first corner.

Grosjean and Maldonado are both into the top ten now, with Ricciardo and Kvyat both dropping out.

The DRS is now activated.

Lap 4

Rosberg is happily setting the pace at the front as he extends his lead to 2.2s over Vettel. Hamilton is 1.1s off Vettel now, outside DRS range.

Massa moves up to sixth ahead of Verstappen. Again into Turn 1.

Grosjean loses two places. To Maldonado in Turn 3 and to Ricciardo in Turn 5.

Lap 5

Rosberg extends his lead again and continues to set quick sector times. 2.7s is now the gap over the Ferrari. Hamilton ups his pace to close on Vettel. He is now in DRS range.

Bottas is 2.2s off Hamilton and has Raikkonen 2.1s behind.

The Toro Rossos continue to move backwards as Maldonado passes Sainz into Turn 1 for eighth place.

Lap 6

Ricciardo dives to the inside of Sainz, it seems the Toro Rossos have got their set-up all wrong for the race. Grosjean is now hounding the Toro Rosso of Sainz.

Lap 7

Hamilton dropped a bit of time to Vettel on that last lap but is now closing in again. Vettel is 4.3s off Rosberg, so if Hamilton wants any chance of winning this race he needs to make his move soon.

Sainz now drops out of the top ten as Grosjean moves past.

Lap 8

Button reports he has already lost the rear tyres. He is down in 18th, Alonso is currently running in 12th and will be the next driver to line up Sainz.

Maldonado passes Verstappen for seventh. He now has a 5.0s gap to Massa in sixth.

Lap 9

Vettel is 5.5s off Rosberg as Hamilton is told "we are thinking of plan B". That could mean a three-stop to get Hamilton ahead of Vettel on some fresh tyres. Hamilton says that is good because he can't get close to Vettel at the moment.

Lap 10

Rosberg is a second faster than Vettel and Hamilton, who are now 6.6s behind. Bottas is keeping just about in touch, 4.2s off Hamilton and Raikkonen is 2.7s off him.

In the next five or six laps we will start to see who is going to gamble on a three-stop. The key will be to find some clear air on track to exploit the extra grip of the fresh tyres.

Lap 11

Hamilton is now right on the back of Vettel again. They are 7.0s off Rosberg, but every time Hamilton comes to a fast corner he drops off the back of the Ferrari in the turbulent air.

Ricciardo attempts a pass on Verstappen for eighth, but runs deep and loses the position back.

Lap 12

Marc asks: "Who caved in Maldonado's rear wing? Surely he could not have managed to crash that himself?"

It may have been contact with Grosjean when he passed him earlier.

Lap 13

Hamilton continues to hound Vettel, but even with DRS he can't quite get close enough. He thought about it into Turn 1, gave Vettel a little warning in his mirrors, but it wasn't enough.

Hamilton told it's Hammertime! I suspect they are getting ready for a pit stop.

Lap 14

Hamilton pits. He takes on medium tyres but it was a 5.3s stop because the left rear was very slow going on. Disaster for Hamilton as he comes out behind Maldonado and loses his gap of clear air.

Hamilton makes quick work of getting past the Lotus but that has lost him somwhere in the region of three or four seconds in total to Vettel.

Lap 15

Vettel pits now and the stop is good at 2.3s.That's three seconds there and he rejoins comfortably ahead of Hamilton despite the Mercedes getting that lap on fresh tyres that the pit wall was hoping would allow Hamilton to leap frog Vettel.

Rosberg will pit next...

Lap 16

Rosberg comes in for a fresh set of medium tyres. His stop is good at 2.5s. Bottas also pits.

Raikkonen now leads, can he try to make a two-stop work? He is good on his tyres, but it's still a big ask.

Maldonado pits and Lotus remove an end plate from the car. That will have ruined his race. The Lotus is now running with just the middle and left support on that rear wing. A replay shows it was contact with Grosjean in Turn 3 that caused the problem.

Lap 17

Hamilton tells his team to come up with another plan as he is not convinced he can beat Vettel now.

Raikkonen pits from the lead and comes back out behind Bottas to resume his race in third. However, he is mixing things up by taking the hard compound tyres.

Lap 18

Rosberg leads Vettel by 5.4s now. Hamilton is 1.1s behind the Ferrari. Obviously lots of radio chatter with the No.44 car as Hamilton tells his engineer not to talk to him in the corners.

Lap 19

Hamilton continues to chase Vettel and he is closing.

Lap 20

This time Hamilton has a look at Vettel into Turn 1. He comes short of attempting a lunge, but Vettel will be very aware of the Mercedes in his mirrors.

Hamilton makes his presence known again into Turn 10. If he is going to pass it needs to be soon.

Raikkonen told his pace is very good and he is asked to put in a stint like Bahrain when he adopted a similar inverse strategy to the cars around him.

Lap 21

Hamilton has another look into Turn 1 to try to pass Vettel, but again is about a car length short of making it stick. He needs to nail his exit out of the final corner and then use all the DRS advantage into Turn 1.

Lap 22

Once again Hamilton fails to make it stick. Vettel is happy to allow the Mercedes to close in the twisty bits but then uses all his his power on the straights.

Alonso pits from ninth. A good stint for him.

Lap 23

Hamilton remains 0.8s off Vettel as they cross the line. This is a good scrap but will not be helping the Mercedes' tyres. Meanwhile, Rosberg is 6.7s down the road and able to take it easy on tyres, engine and fuel.

Kvyat passes Verstappen for ninth place as both Red Bulls return to the top ten ahead of both Toro Rossos.

Lap 24

Hamilton has perhaps given up for this stint as he arrives in Turn 1 a fair way off Vettel this time. Back to tyre preservation ... for now.

Lap 25

Marc says: "Kimi vs. Bottas…Kimi's testiness this weekend comes on the heels of the Bottas rumors. Not saying they are connected, but he needs to pass him."

Maldonado contines to circulate back in 18th without a rear wing endplate. It appears to be holding up okay, which shows just much work the middle support does on these cars.

Rosberg was 0.4s slower than Vettel on that last lap.

Lap 26

Now Rosberg ups the pace again, so perhaps it was a slow lap behind some Manors.

Button is still struggling: "As soon as I touch the throttle I have wheelspin". He now has Maldonado's Lotus filling his mirrors. Let's hope they don't make contact again like in China.

Lap 27

Hamilton has now dropped to 1.3s off Vettel.

Alonso pits, which is disappointing after his late stop in the first stint. Alonso goes straight through his pit box. It looks like a brake failure. Fortunately his front jack man got out of the way just in time.

That is the end of Alonso's Spanish Grand Prix.

Lap 28

Rosberg's gap is now 6.1s as he comes across traffic.

Button pits successfully so at least one McLaren is still in the race.

Lap 29

Now Rosberg gets his foot down and extends the gap to 7.2s. It looks like he is managing this race from the front.

Bottas is 9.5s off Hamilton and has Raikkonen 11.1s off him. Good pace from the Williams on a weekend where it looked like they had not matched the top two for updates on the car.

Lap 30

Rosberg is comfortable now with an 8.0s lead. Hamilton remains one second off the back of Vettel and has stopped putting the pressure on the Ferrari.

Bottas reports slightly more rear deg.

Lap 31

Meanwhile, Raikkonen picks up the pace again. It may be that the hard tyres longevity means they are now the better tyre to be on.

Rosberg is 8.7s clear of Vettel now and it seems Hamilton is lining up for another pit stop to undercut Vettel.

Lap 32

Hamilton wasn't helped by traffic on that last lap, so needs to close the gap again to Vettel if he is going to pit and make an undercut work.

Lap 33

Hamilton pits this lap. The hard tyres are coming out of the garage. That will be another set of new tyres. If they are to go to the end of the race he needs to make them last 33 laps, which is unlikely. I would say he is still on a three-stop.

Massa also pits from sixth. He was 6.8s off Raikkonen but is on a different strategy.

Lap 34

Hamilton rejoined behind Raikkonen but passes the Ferrari into Turn 1 with ease. That's the difference of 14 laps of degradation on the hard tyres.

Hamilton now sets a fastest first sector of the race with some clear air. Will Ferrari react by pitting Vettel?

Lap 35

Rosberg's lead is now up to 10.5s. He seems to have this one in the bag.

Hamilton goes 2.3s faster than Vettel on that lap alone. Impressive on the new hard tyres. Ferrari must pit Vettel soon.

Button will be reassured to hear he is not suffering from the same brake problem as Alonso.

Lap 36

Vettel told that Hamilton is on three stops, which suggests Vettel is aiming for a two-stop strategy. That explains why Ferrari are reluctant to react to Hamilton's quick times. Hamilton is 17s behind Vettel, so it could still become interesting in the final stint with Hamilton so much faster per lap.

Lap 37

Rosberg, meanwhile, is 12.1s ahead of Vettel. Bottas is 10.8s behind Vettel and seemingly doing rather well. He has Hamilton gaining on him at three seconds a lap behind him, which should mean he is passed in the next two laps.

Raikkonen remains on a quicker pace that Bottas and a pace to match his team-mate. But Raikkonen will be on the quicker tyres for the final stint.

Lap 38

Hamilton is still over two seconds faster than Vettel on that last lap. This will be interesting no matter what Ferrari do with their strategy. My money is on Hamilton.

Lap 39

Hamilton passes Bottas into Turn 1. The Williams could not put up a fight on its old tyres. Meanwhile, Raikkonen is told he is closing on Bottas and fourth place by the end of the race.

Lap 40

Rosberg's times remain impressive. He set a 1:31.5 on that last lap, which is 1.4s faster than Vettel and 0.2s quicker than Hamilton on the newer hard tyres. However, we should point out that Hamilton had traffic on that lap.

Lap 41

Ferrari are ready for a pit stop... It's Vettel and it's done in an impressive 2.2s. He rejoins down in fourth, behind Bottas and ahead of Raikkonen. It's the hard tyres for Vettel with 24 laps remaining.

Lap 42

Slow stop for Gorsjean as he overshoots his marker. The front jack man flies back two or three metres, but remains on his feet. A slow stop as a result from eighth place.

Raikkonen pits from fifth too.

Lap 43

Now Bottas pits. A good stop and he takes on hard tyres in just 2.5s. Raikkonen took on medium tyres - the fresh ones we were talking about earlier - and will now hope to attack Bottas.

Lap 44

Hamilton continues to pump in fast times as he tries to make the most of this stint. He is 14.5s ahead of Vettel but we think needs to make an extra stop. The only downside for Hamilton is that Vettel also has fresh hard tyres now.

Rosberg, meanwhile, is 23.0s ahead at the front and cruising towards his first victory of the season.

Lap 45

The other possibility is that Hamilton does a monster stint on these tyres of 33 laps (half the motor race) and takes the fight to Rosberg... Even if he did Rosberg would have fresher tyres.

Lap 46

Rosberg pits now. He has a stop of 2.8s for hard tyres. He returns to the track behind Hamilton, with 20 laps remaining, but Mercedes confirms Hamilton will indeed pit again.

Hamilton has a 16.0s lead over Vettel and it's growing. He'll need more than 23s to hold that lead at the next pit stop, so most likely he will come out behind on fresher and softer tyres after his final pit stop to attack the Ferrari.

Lap 47

Raikkonen is all over the back of Massa now and needs to find a way past.He does that with relative ease into Turn 1. Now he can attack the 8.0s gap to Bottas.

Lap 48

Maldonado retires from the race.

Hamilton has a 2.7s lead over Rosberg, which is growing and now has 20.1s lead over Vettel. That has gone up much quicker than I thought, so clearly the Ferrari is not as happy on the harder rubber as the Mercedes even when it's new.

Lap 49

Hamilton extends his lead to Vettel to 21.7s. Raikkonen now has the gap to Bottas down to 6.4s and is closing at 0.7s a lap. That should turn into a nice fight by the end of the race.

Lap 50

Rosberg is now the faster of the two Mercedes and closes the gap to 2.2s. Hamilton will pit soon as he has his lead over Vettel to 22.7s which is more or less enough to come out in front. If not, he'll have much quicker tyres on his car to overtake.

Raikkonen gets the gap to Bottas down to 5.8s. Massa is a further 26.0s down the road and Ricciardo is another 26.4s behind the Williams. Grosjean may have a fight on his hands from Kvyat while Verstappen holds onto the last points position in tenth.

Lap 51

Hamilton pits this lap as Rosberg appears in his mirrors. A decent stop for Hamilton at 2.6s and medium tyres are fitted.

He comes out comfortably ahead of Vettel's Ferrari and will only extend his lead now he is on those medium tyres with 15 laps remaining.

Lap 52

Raikkonen was slower than Bottas on that last lap and the gap remains at 5.8s.

Lap 53

Hamilton is 20.6s off Rosberg now. I can't see him closing that gap in the remaining time, especially with Rosberg clocking a 1:29.1.

Hamilton sets a 1:28.4, so that won't be enough to close the gap unless Rosberg's tyres really drop off.

Lap 54

19.9s is the gap with 13 laps remaining. Vettel drops to 7.4s off Hamilton and will now be looking behind him with Bottas 0.7s faster per lap and 8.9s off. Raikkonen is 4.1s off Bottas and closing at 0.8s a lap on the Williams.

Lap 55

Hamilton goes a second faster than Rosberg on that last lap. 18.9s is the gap, but still I don't think it will be enough.

Vettel says "Come one, blue flag!" He is struggling to get through the traffic as Bottas is 8.3s off. Meanwhile, Raikkonen is 1.3s quicker than Vettel per lap and 11.7s behind. That could get interesting if he can pass Bottas quickly.

Lap 56

Raikkonen closes the gap to Bottas to 2.7s, but this is when it gets tricky as the Ferrari starts to arrive in the turbulent air behind the Williams.

Kvyat's charge against Grosjean seems to have lost some of its steam as he sets the slowest lap bar the Manors on that last lap.

Lap 57

10 laps remaining and Hamilton is 17.2s off. Mercedes tells him to look after his car and consolidate the position. Hamilton asks if it's "Impossible", but is told Rosberg will only up his pace.

Raikkonen is now right behind Bottas as the Ferrari passes the lapped Toro Rosso that was separating them on track.

Lap 58

Vettel is still 0.9s slower per lap than his team-mate as Raikkonen arrives in DRS range of the Williams.

Raikkonen appeared to have a go at Bottas into Turn 10 and messed it up. The cameras cut to some beer drinking fans, which was useful.

Lap 59

Raikkonen isn't close enough to make a move into Turn 1 on this lap, remember that Williams is very fast in a straight line.

Hamilton is still going for it and closing on Rosberg. But 13.6s in seven laps still seems too much. Unless of course the lead Mercedes has a problem.

Lap 60

Raikkonen goes sideways through the final corner and as a result got nowhere near into Turn 1 on the next lap. He needs to nail that corner exit to make this work as the Williams is not hanging about on the straight even if it is slow in the corners.

Now they come up behind traffic too. The Ferrari continues to struggle on its tyres.

Lap 61

Raikkonen can't make this work at the moment. Bottas is keeping a cool head and is focusing on a good exit to the final corner and plenty of Mercedes power down the straight. Raikkonen needs to change tack and try somewhere else, although that is very tough on this track.

Lap 62

The traffic also seems to be playing into Bottas' hands at the moment. Kvyat meanwhile, has closed to within a second of Grosjean. The two Toro Rossos are also battling over the final point with Sainz all over the back of Verstappen.

Lap 63

Sainz passes Verstappen into Turn 1 to take 10th. Raikkonen continues to toil away behind the Williams. It looks like he may well struggle in a similar way to how Vettel struggled in Bahrain.

Lap 64

Hamilton has cooled off his pace. He is 0.8s slower than Rosberg on that last lap but has no reason to worry with a whopping 28.7s lead over Vettel in third. Bottas is 12.4s off Vettel and Raikkonen 0.6s behind Bottas.

Lap 65

I can't see this happening for Raikkonen. With every lap that passes, his tyre advantage over Bottas wanes and he is currently nowhere near passing him into Turn 1.

The gap from Rosberg at the front and Vettel in third is 44,0s. Who said the era of Mercedes domination was over?

Lap 66

At the front Rosberg wins by 17.5s from Hamilton and 45.3s from the closest Ferrari of Vettel.

Bottas holds off Raikkonen to take fourth. Sainz did get ahead of Kvyat for ninth, but will the stewards have something to say about that last lap overtaking attempt at Turn 1. I'd like to see it again to pass comment.

A replay shows that Sainz went to the outside, but Kvyat was the one who locked up and arguably caused the contact. Sainz then ran deep and the stewards are investigating what happened later as Sainz rejoined in front of Kvyat after leaving the track. I'm with Sainz on that one as I believe he was forced off by Kvyat's mistake, but I didn't see how he rejoined the track.

Another one-two victory for Mercedes, making it three out of five. But most significantly it was the first for Rosberg, which rather changes the dynamic in the championship. Even better, we have the pressure cooker that is the Monaco Grand Prix circuit for the next round of the championship.

Vettel seems happy enough with third, but a gap of 45.3s to Mercedes on such am aero-dependant circuit will not go down well in Maranello.

Thanks for joining us for the Spanish Grand Prix. Plenty or reaction to come so make sure you keep checking back to hear what the drivers and teams had to say.