Sauber's Marcus Ericsson:, external Morning session done. No problems with the car, and a positive feeling! Soon time to drive again.

Image source, PA

It's been a while, but Sebastian Vettel is back out on track and immediately down to business. The four-time champion goes third quickest, nine tenths slower than pace-setter Nico Rosberg and just a few thousandths behind Williams' Valtteri Bottas.

F1 journalist Dan Knutson in Jerez: "McLaren crew members have been unloading large items wrapped in bubble wrap, plus boxes and small crates out of a van next to the team transporters. It's obviously a shipment of the latest bodywork bits and other parts fresh from the factory in Woking."

Andrew Benson
Chief F1 writer

Image source, Getty Images

"Not that a new F1 driver needs any more motivation, but Toro Rosso's Carlos Sainz Jr not only has a place to carve in the sport but also a chance to prove a point to his employers. Red Bull initially passed the Spaniard over in favour of team-mate Max Verstappen, who was only signed up into the Red Bull junior driver programme a matter of a few weeks before he was promoted to F1, and it was only when Sebastian Vettel told them he was moving to Ferrari, leaving a vacant slot at Red Bull into which Daniil Kvyat was slotted, that Sainz was finally given the call.

"That has been parked in a corner for now, though. 'There is a lot of concentration, a lot of will to go out on track, and so far the team has done a good job to prepare us for this season,' says Sainz, who is a friend of Fernando Alonso. 'Everyone is very positive which gives you a lot of good feelings. At the moment there are no nerves, just looking forward to working with them, try to do a good job and to arrive at the first race as well prepared as possible.'"

Toro Rosso's Carlos Sainz Jr puts a flurry of laps together and improves to go fifth quickest, 2.2 seconds off the pace. He has Nico Rosberg and Valtteri Bottas for company at the moment.

While most of the field are busy getting down to work for the new season, Nico Hulkenberg is taking it easy. Force India aren't in Jerez, after choosing to skip it so the German has spent the morning watching the Australian Open final.

"Great #AusOpenFinal! Congrats @DjokerNole! But respect to @andy_murray for the fighting spirit! tweeted Djokovic., external

Alex Withington:, external Is Rosberg going to drive all the way to Melbourne? Impressive start from Mercedes - fast and reliable.

Nico Rosberg didn't waste much time with lunch - the German is back out there, improving his lap tally to 76 for the day and remains fastest. Impressive stuff.

Andrew Benson
Chief F1 writer

Image source, Getty Images

"Toro Rosso have been particularly bullish, if you'll pardon the pun, about their prospects this season. The boss of Red Bull's junior team, Franz Tost, says the car is 'a strong package; we have made a lot of progress. It's the fastest car Toro Rosso has ever built'.

"Tost played down lack of experience of their all-rookie driver line-up of Carlos Sainz Jr and Max Verstappen by saying they had been 'racing for 10 years'. But he rather undermined his own argument when he added that in this test it was vital they do 'a lot of laps so the drivers can learn the car and the tyres'. The team have targeted an ambitious fifth place in the constructors' championship, which 'means the drivers have to be permanently in the points', Tost points out."

After a late start Williams are plodding along nicely with Valtteri Bottas up to fourth in the timesheets, two seconds off the pace.

Image source, Nico Rosberg

Nico Rosberg is loving his time in the new car so much, he's even having his lunch in it...

Image source, Getty Images

Three teams unveiled their 2015 machines this morning, which means we've seen all nine cars set to contest this year's World Championship. That's not including Caterham and Marussia, who look set to miss the season. Nico Rosberg and Lewis Hamilton posed for photos, but not before taking a selfie first.

Andrew Benson
Chief F1 writer

"As an illustration of how far the teams have moved on with the new turbo hybrid engines, it's interesting to compare the laps completed on this first day of 2015 testing, with the first day of testing before 2014, when the engines were brand new. Back then, Ferrari's Kimi Raikkonen did the most laps, with 31.

"Twelve months on and Nico Rosberg has already racked up 60 laps in the Mercedes, and there are still over four hours to go. That underlines why McLaren, whose Honda engine is brand new, are saying they don't expect to do many laps at the start of the test."

Image source, Sauber

Sauber:, external Encouraging morning for Sauber C34.

It's all gone quiet on track - perhaps some of the teams are grabbing a spot of lunch...

Valtteri Bottas puts Williams on the timesheets with a 1:28.479. That puts the Finn sixth, just behind Toro Rosso's Carlos Sainz Jr.

Image source, Williams

Williams:, external Good crowd here.... It's still pretty cold though despite the sun!

Image source, AP

Red Bull have pulled a blinder with their zebra-like testing livery. Daniel Ricciardo is currently second quickest, 1.5 seconds off the pace. His team-mate Daniil Kvyat will take the wheel tomorrow.

Image source, Williams

Williams:, external Valtteri remains in the car as we get ready for some more laps.

Nico Rosberg has the track to himself at the moment, the German sealing his half century of laps as the day continues to go to plan for Mercedes.