Ahead of today's opening session, the ait temperature is 38 degrees C, while the track temperature is 47 degrees, somewhat different to seven days ago.

For the third successive day it is the exploits at McLaren which dominate the headlines, though sadly it is not in terms of the Woking outfit making progress, rather the move which sees Fernando Alonso contesting the Indy 500 next month.

Earlier this morning the Woking team confirmed that Jenson Button will replace the Spaniard in Monaco, stressing that this is a one-off move.

This weekend sees the resumption of friendly - according to Lewis Hamilton - hostilities between Mercedes and Ferrari, or at least the Briton and Sebastian Vettel. Teammates Valtteri Bottas and Kimi Raikkonen are both in need of strong results after China, the Mercedes Finn making a self-confessed "stupid mistake" while the Ferrari Finn didn't try hard enough, according to the company president.

While the majority of updates won't appear until Barcelona, this weekend should give us further insight into the true pecking order, and while Red Bull needs to close the obvious gap to the leading duo, it is the battle for supremacy in the midfield which continues to excite.

Talking of updates, Ferrari has brought a number to the desert, not least a new front wing and new floor. Indeed, the very notion of updates at one of the opening flyaway races makes clear the Italian team's determination this season.

Making his first appearance in the F1 paddock this year is Bernie Ecclestone, a sight that will surely send a chill through some of those who have taken full advantage of the former 'headmaster's' absence in recent months.

Because this session takes place earlier than qualifying and the race, in many ways this session is fairly unimportant in terms of data acquisition for this weekend, however, it can serve its purpose as a general test session.

Remember, next week sees two days of testing which gets underway on Tuesday.

As Ericsson heads down the pitlane to get proceedings underway, the front wing on Alonso's car gets a generous coating of flo-vis.

Verstappen is another of the early risers, the Dutchman's Red Bull sporting a large sensor gate on just one side of the car.

More and more drivers head out, all on mediums bar Sainz who is on softs, the Spaniard having taken a huge gamble at the start of last weekend's race, the only driver to start on slicks.

As Stroll heads out, also on the softs, he is followed by Wehrlein, who is back in the Sauber for the first time since FP2 in Melbourne.

Five minutes in and all but the Mercedes duo have appeared.

Ricciardo posts the first time of the weekend, the Australian stopping the clock at 1:38.985.

"Many drivers taking advantage of this session to use the medium compound, not seen in China," admits Pirelli.

Bottas finally heads out as Ricciardo improves to 38.843, leaving Hamilton as the only no-show.

As Hamilton finally heads out - 11 minutes into the session - Bottas has his work cut out controlling a very lively Mercedes. The Finn subsequently posts 39.757.

Hamilton posts an ultra-safe 59.276 before improving to 38.112, leapfrogging his teammate who had just improves to 38.246.

"As expected, you can see overheating through T12 and 13," Bottas is told as the camera cuts to the Force India of Perez which is smothered in flo-vis.

As Stroll posts the fourth time of the day (38.553), Hamilton posts 37.355 and Bottas 37.473.

Vettel heads out, the German running the old front wing while Raikkonen tries the new. Neither driver is running the new floor at this stage.

A 38.086 sees Peres go fourth while Grosjean posts 39.081 to go sixth.

Masa goes third (37.625) as Hamilton improves to 36.708.

A 36.934 sees Vettel go second on his first flying lap, just 0.226s down on his fellow championship leader.

Stroll complains that he is getting the 'Safety Car' warning. "It keeps going yellow!" He is told to press the SC button on his steering wheel. Fellow slaves to IT will empathise with the Canadian.

A 36.079 sees Sainz go quickest, the Spaniard still on the softs. Those on the mediums - which means pretty much everyone else - are all complaining about a lack of grip.

At which point, Pirelli admits: "As usual not a lot of grip in the early part of this session. Track is normally dirty in FP1 also due to sand from surrounding desert."

Thirty minute in and all but Raikkonen have posted a time, though the Finn is on track.

Raikkonen can only manage 45.759 after making a mistake in S2. However, no such issues for Bottas, the Finn going quickest in all three sectors (on softs) to post 35.002.

Hamilton is the third driver to make the switch from mediums to softs, as Raikkonen improves to 42.333 but remains 20th.

Hamilton posts 34.636 on the softs as Raikkonen slow down, smoke billowing from the back of the Ferrari. "We need to slow down," the Finn is told but in fact he pulls off to the side of the track. A worrying start to the weekend for Ferrari.

Replay shows the lights on his steering wheel going out just before the engine issue. Then again, why was the Finn running so off the pace beforehand anyway.

As he walks into the desert en route back to the paddock, Kimi resembles a Power Ranger on a mission.

As the Ferrari is lifted on to the back of a truck and the majority of drivers hand back a set of tyres, the Mercedes duo remain on track.

Finally a scooter arrives to collect Raikkonen who was making his way back on foot. In his overalls and with his helmet still in place, the Iceman must have been melting.

Check out our Friday gallery from Bahrain, here.