So that's good stuff from Mercedes and good stuff from McLaren, but what's going on at Ferrari?

Kimi Raikkonen spent some of this morning doing aero work but hasn't been out on the track for a while now and has done just 15 laps - the fewest of all the drivers today...

The pole lap for the Spanish Grand Prix on this circuit last year was 1:22.000, by the way.

Now then!

Valtteri Bottas has spent the morning totting up the lap counter but has just strapped on a set of supersofts and he's on a quick lap now. It's not just quick, it's very quick as he blitzes a 1:19.310.

That's the quickest lap we have seen so far in testing this year, four tenths quicker than the previous best set by Bottas last week.

Fernando Alonso stays out to complete a few laps in a row after posting that considerably more competitive time. He heads in after completing lap number 20 - that's more than Kimi Raikkonen and Carlos Sainz. So far so good.

McLaren spent the first couple of hours of this morning in and out of the pits, with Fernando Alonso only doing a couple laps at time, and slow laps at that. 

Whatever their plan was, it appears it was a success as they have moved into putting a first meaningful time on the board. Alonso does a 1:23.210 on softs to climb to third.

A stonking lap from Nico Hulkenberg!

The German, with supersofts on his Renault, produces a 1:21.213 to leap up to second, a hundreth of a second quicker than Valtteri Bottas, who did his personal best on ultrasofts.

Here's Wais Kuba's predictions for the fastest three cars in 2017.

I'm actually quite surprised by the amount of people that aren't expecting Mercedes to power away with it this season.

Fancy having a crack at predicting the top three fastest and slowest drivers? Head here.

Image source, .

Valtteri Bottas, on 34 laps for the day, pops out to join Felipe Massa on the circuit.

The track is empty apart from one car. Whose is it? It's Felipe Massa's. Of course it is. 

The Brazilian has done 39 laps in the space of two hours, more than any other driver. Collecting as much data as possible so Lance Stroll can spend his time this afternoon familiarising himself with the Williams?

Andrew Benson
Chief F1 writer

It’s been a slow start to the day for Fernando Alonso and McLaren-Honda on the sixth day of a trying pre-season programme. 

The multiple problems Honda have had have raised questions about when - and indeed whether - Honda plan to introduce the updated specification of engine that was promised last week. So, I asked Honda whether it was still the plan to run it. 

“We are not able to disclose the current PU spec we are using today nor the timing to use the updated spec at this moment,” a spokesman said. “It is sure we are to use it within this week as Eric (Boullier) mentioned, though.” 

And would they tell us when they do run it? “I'm sorry but we cannot confirm it at this moment either.” 

In, out, shake it all about. 

Things going according to plan, according to McLaren.

Image source, McLaren

We were wondering earlier what the most amount of laps a driver has done in a single day of testing, has Fabi found the answer?

Drivers in bold have posted improved times in the last hour.

1) Max Verstappen (Red Bull) - 1:20.516 - soft 

2) Valtteri Bottas (Mercedes) - 1:21.229 - ultrasoft

3) Felipe Massa (Williams) - 1:21.618 - soft

4) Kimi Raikkonen (Ferrari) - 1:22.926 - medium

5) Carlos Sainz (Toro Rosso) 1:23.569 - supersoft

6) Sergio Perez (Force India) 1:24.059 - medium

7) Romain Grosjean (Haas) 1:24.301 - medium

8) Nico Hulkenberg (Renault) - 1:24.417 - medium

9) Pascal Wehrlein (Sauber) - 1:24-851 - Medium

10) Fernando Alonso (McLaren) - 1:34.732 - ultrasoft

Very bitty morning for McLaren. Fernando Alonso has been popping out for one, maybe two laps at time before heading back in again. The Spaniard is yet to post a competitive time, with his 1:34 still propping up the timesheet.

We have a change at the top of the order. 

Max Verstappen is fastest of all through the first sector and keeps that up for the rest of his lap, posting a 1:20.516 - seven tenths of a second quicker than Valtteri Bottas' time. 

Verstappen's lap came on the softs whereas Bottas did his on ultrasofts.

McLaren racing director Eric Boullier explained to Formula1.com, external  why Honda have such big problems in matching the other engine manufacturers. This is what he had to say:

"Because they are still three years behind in time to the others: Mercedes, Renault and Ferrari started in 2010 - and all these three started with an existing organisation, as all three were already doing F1 engines. In 2013 Honda decided to come back to Formula One and started from scratch: empty buildings! They had to buy everything - and find the right people. So to be fair you have manufacturers who had seven years and are still struggling - and Honda started four years after the others. 

"These units are so complicated that you have to be really process driven and go step by step. Unfortunately there is no short cut."

F1 journalist Dan Knutson in Barcelona: On race weekends there is a curfew that limits the number of hours the crews can spend at the track. There are no such restrictions, however, during tests and the teams work around the clock.

Team principal Guenther Steiner explained how it works at Haas: “We have a day and night shift. You have people coming in around 6 p.m. and have dinner with the guys from the day shift, so they exchange what they learned and know what they have to do. The night shift guys take over and work until the sun comes up, then the day shift comes in again and you do the same thing. They have breakfast together and some go to sleep and the others go to work.”

Blaise Tahar: How long will Alonso's patience hold out if McLaren-Honda don't improve? Will he see the season out?   

David Barker: Is Alonso dragging a caravan, whats the use of lapping 10-15 seconds off the pace.