I can't quite believe that we're almost seven hours into testing and we've only had one red flag. Mercedes have certainly had the best day, with Williams, Toro Rosso and Sauber getting a decent number of laps on the board.

Ferrari and Red Bull have had little niggles but still got more than 30 laps under their belts.

McLaren have been less successful, with just six laps - but they're playing catch up after a disappointing run in Abu Dhabi, where they managed just five laps.

The team have put together a photo gallery of all this year's new cars, which is very much worth a look. You can find it here.

Just Marcus Ericsson on track at the moment in the Sauber with one hour and 15 minutes left of today's session. Sebastian Vettel remains fastest in the Ferrari.

It's a family-affair for Nico Rosberg, Carlos Sainz Jr and Max Verstappen today with their fathers Keke, Carlos and Jos in Jerez keeping an eye on proceedings.

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There's only one man the majority of the fans in Jerez want to see - and that's Fernando Alonso in the new McLaren. Unfortunately, the Spaniard has only managed a handful of laps.

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Valtteri Bottas has made his half century, only the second driver to do so after Mercedes' Nico Rosberg. Good stuff from the Williams team after a delayed start to their running. Sauber have done a decent job, too, clocking up 40 laps.

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While McLaren struggle, Mercedes continue to cruise along with Nico Rosberg now having completed over 120 laps. Today couldn't have gone much better for the reigning world champions.

We've not seen McLaren and Fernando Alonso for a while. The team report they are "tracking down a niggly problem - which is taking some time. Hope to be out again before the end of the day."

Stuart Gill:, external Big fan of the Red Bull's livery at testing. Would be awesome if they keep it for the season!

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It's a really impressive turn out in Jerez, with grandstands packed with fans keen to see the 2015 cars in action for the first time.

Daniel Ricciardo continues clocking up the laps, the Australian - who finished an impressive third in the drivers' standings last year - moving into third place on the timesheet, 0.380 seconds off the pace set by Ferrari's Sebastian Vettel.

F1 journalist Dan Knutson in Jerez: "There are signs of activity in the Lotus garage as crew members are organising tyres and the tyre trolleys."

Image source, Getty Images

The Red Bull, in it's brilliant zebra-style livery, is back out on track, with Daniel Ricciardo behind the wheel. It's another excuse to show you a pic of the car.

After a lull in the action, Valtteri Bottas heads back out on track in the Williams. The Finn gets company in the form of Ferrari's Sebastian Vettel.

F1 journalist Dan Knutson in Jerez: "The Renault engine was fired up in the Red Bull, so it looks like the team has solved or nearly solved whatever the problem was that has kept the car in the garage for so long."

Ferrari say system checks were the main items on the programme "which was altered mid-morning, to improve the radio communications between team and driver".

The team add: "The decision was therefore taken to bring forward the lunch break, so as to resume the planned programme for the afternoon."

Andrew Benson
Chief F1 writer

"There has been a great deal of discussion about Red Bull's decision to parachute Max Verstappen into F1 at the age of 17 - making him the youngest F1 driver ever by about two years - and after just one year in car racing. The decision has prompted governing body the FIA to introduce new criteria for F1 'super-licences' for drivers. These will be introduced in 2016 and among them are that the driver cannot be younger than 18 - which of course means Verstappen would not have qualified if they were in force now.

"That's a tacit admission that even the FIA has doubts about the wisdom of Red Bull's decision. Toro Rosso team boss Franz Tost is dismissive of the issue, however. 'We had the same nonsense with Daniil Kvyat last year,' Tost said, 'and he drove a fantastic season and is racing for Red Bull this year. So I don't care what people are saying.' That rather misses the point, however - Kvyat was neither 17 nor did he have only a season's car racing behind him. It will be fascinating to see how Verstappen copes with the pressures of F1."

Sebastian Vettel heads back to the pits after that scorcher of a lap, leaving the track quiet with a little under three hours to go on the first day of pre-season testing.

Sebastian Vettel goes quickest with a 1:22.999 in the Ferrari. Nico Rosberg is second, 0.1 seconds off the pace, with Valtteri Bottas' Williams eight tenths further back.

F1 journalist Dan Knutson in Jerez: "Nico Rosberg has now done more laps - he's heading for the century mark - than all eight drivers combined on the first day at Jerez last year."