Don't forget to tune into BBC Radio 5 live for all the chat from the paddock. You can listen via this very page.

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Andrew Benson
Chief F1 writer in Barcelona

As much as Honda’s current travails and his Indianapolis adventure are topics for Fernando Alonso at the moment, so too is his future. The driver market ‘silly-season’ has already started, with rumours that Sebastian Vettel has some kind of pre-contract arrangement with Mercedes - which he laughed off, but did not deny - and Alonso is inevitably at the centre of it, as his contract with McLaren expires this season. Could he even consider going back to Ferrari, he was asked earlier this week?

“Around September or October I will need to consider what I will do next year,” Alonso replied. “If it’s time to find other challenges outside Formula 1 or if Formula 1 will be an opportunity to win the championship, which is my main goal. I’m very open to anything. I think with this year’s cars and the 2017 regulations, the cars are good to drive. I think Formula 1 is back in a way. We see this real power of efficiency, corner speed, things we were missing in the last couple of years. The cars look nice from the outside, with the big tyres, everything, so I like this Formula 1.

“So my intention or my first priority is to race next year here and not only to race, I want to win. Now that I have not any more obligations with McLaren… I’m happy with the team, but we are not winning, so if from here to September or October we are in a position where I see clearly a possibility to win in 2018, I will be more than happy to stay with the team. If it’s not the case, I will be more than happy to talk to anyone.”

After a brief virtual safety car period we are properly up and running once again.

Felipe Massa put a time on the board before that spot of bother for Fernando Alonso, clocking a 1:25.894.

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"Put some sand there," Fernando Alonso directs with his finger. The marshals lob a load of sand over the oil on the track that has leaked out of his McLaren.

I wouldn't blame Alonso is he tells his team he is just bobbing out for a coffee and instead goes and grabs an early flight to America.

Ben Ashcroft: Three corners for @alo_oficial, external today. This is just getting more and more depressing.

Bethonie Waring: Amazing how @alo_oficial, external and the team keep up the motivation and keep going. Must be so depressing.

Fernando Alonso was on his out-lap when trouble hit. He's out of the McLaren now inspecting the rear with a group of marshals. 

"Engine. Engine problem," says Alonso. 

Shocking start to the weekend at his home race. The Indy 500 probably can't come soon enough...

Uh oh spaghettios, there's a problem for McLaren already. 

Fernando Alonso has come to a stop with smoke coming out his car...

Mercedes duo Lewis Hamilton and Valtteri Bottas head out onto the track for the first time this morning and we've now had everyone out for at least one lap.

No times yet, though, 10 minutes in.

Tom Clarkson
BBC Radio 5 live commentator

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This [different liveries] was tried in F1 back in 1999. British American Racing tried to run the cars in different liveries, they launched the cars in different liveries but the FIA thought better of it. They feel pretty strongly about that one.

Amit Madalia: Had a thought on the numbers to make cars easy to identify... why not let cars in the same team run in different liveries?  

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It's not just about upgrades in Barcelona because teams are also kicking off the traditional start of the European season with a new look. 

From this weekend onwards, teams have to ensure that the drivers’ names and numbers are more easily seen by fans.

The FIA has deemed that the size of numbers on their liveries now have to be at least 180mm high with a stroke thickness of 30mm. 

Red Bull have opted to whack a great big number on their shark fin. The Red Bull also finally gets a tail as well.

And away we go with 90 minutes of first practice.

Several cars head on out for their installation laps, among them Sebastian Vettel in the Ferrari and Max Verstappen in the Red Bull.

No movement yet in the Mercedes garage.

Andrew Benson
Chief F1 writer in Barcelona

This is traditionally a race of the first big upgrade of the season, and so far Mercedes have made the most impact. The world champions have introduced a massive aerodynamic upgrade for this race, including a narrower nose, underneath which is snow plough-style aerodynamic shaping device, and new bits and pieces pretty much everywhere, including shaving some more weight off a car that the team admit is heavier than they would like. Claims of a shorter wheelbase, though, were dismissed by the team as “not accurate”.

Valtteri Bottas said: "It is a tight battle with Ferrari, it is all about the details. Every single bit counts, and definitely we are trying to develop the car as quickly as we can, with all the new bits. But there is also a lot of performance every weekend. At the moment we need to perform with every compound of tyre in the optimum window, and that is something that Ferrari has been doing better since the beginning of the year.

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So then, upgrades. Red Bull have brought a number of new parts that they hope will bring improved grip and reduced drag.

"We have quite a few different aerodynamic parts on the car," Red Bull team principal Christian Horner told BBC Radio 5 live. "You will notice mainly around the mid-car section where a lot of focus has gone into."

They are not the only ones with big updates here, though...

BBC Radio 5 live sports extra

Commentary is LIVE now on BBC Radio 5 live sports extra with just three minutes to go until first practice gets under way.

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Valtteri Bottas became fifth Finnish winner when he won in Russia and that got us all nostalgic about previous race winners from the tiny country. You can read Jamie Strickland's feature on fantastic Finns here.

So who does Bottas think is the greatest Finnish driver of all time?

"Mika Hakkinen was special," he told BBC Radio 5 live. "When I was a kid he was a hero, and the motivation that kept me going to try harder.

"He was really happy after [my] win, and maybe even little bit emotional. Not normal for a Finn."

Who do you think is the greatest F1 driver from Finland and why? Let us know via #bbcf1

Andrew Benson
Chief F1 writer in Barcelona

Mercedes or Ferrari? That’s the question ahead of every race this season and it’s so finely poised it is impossible to predict. As Sebastian Vettel said: “Mercedes won the last race, we won the last pole. The race before it was the other way around. It is very close, I don't think there is a definite answer. We should hit the track and see.”

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A quirky fact about the Spanish Grand Prix - no single driver has won it twice since 2007, that's 10 different winners in 10 years. 

Valtteri Bottas won his first race in F1 at the Russian Grand Prix last time out, could he become the 11th different winner this weekend?

Andrew Benson
Chief F1 writer in Barcelona

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It rained on Thursday at Montmelo, where the Circuit de Catalunya is situated in the Valley region north of Barcelona but Friday has dawned glorious and a lovely day is in store, notwithstanding the threat of some showers later on. Perfect weather, in other words, to settle back and enjoy the start of the European season on this now-venerable circuit. 

There is a dramatically different Mercedes, tweaks to the Ferrari and Red Bull and many other cars up and down the pit lane, and the next stage of a thrilling title battle is about to slowly unveil itself before our eyes.