Kev: One of my colleagues at another office outed themselves as an F1 nut by getting something published on the F1 testing stream earlier. We should both be working and he/she knows it. I won't tell if they don't though...

Intriguing!

Lance Stroll has taken over from Sergey Sirotkin for this afternoon and he's up and running with a 1:36.800 on softs.

Freddie Skeates: What's the opposite of sandbagging? Whatever it is McLaren are doing it

Kayleigh: Boom, get in Stoff! 100 laps so far

Kevin Magnussen has nudged Lewis Hamilton down to third having done a 1:21.135 on softs.

It's been a very good day for McLaren, but not quite perfect.

Stoffel Vandoorne has just had a brief trip into the gravel. No major drama, though and after a brief return to the pits for a check over, he is back on track now.

Image source, Getty Images

Sam de la Bertauche: Where’s the evidence of McLaren doing good? I’ve seen average times on a tyre compound 3/4 compounds softer than everyone else. Even with a Mercedes engine they were average. They ran most downforce last year making Honda look even worse than it was, to inflate the chassis.

Lewis Hamilton is up to third with a 1:21.241, putting him within two seconds of Stoffel Vandoorne. A reminder that Vandoorne did his time on the hyper-softs while Hamilton is on the slower mediums.

Marcus Ericsson's work is done so Charles Leclerc jumps into the Sauber for this afternoon.

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Dan Knutson
F1 journalist in Barcelona

Four-time world champion Alain Prost attended the test in his role as advisor to the Renault Formula One team. He scored 51 Formula 1 victories during his career including one at this track 1993.

Image source, .

Lewis Hamilton is on the mediums and he begins his day with a 1:27.200 - the 10th quickest time.

The reigning world champion improves on that immediately, clocking 1:22.779 to move up to fifth.

Stoffel Vandoorne is back out on the hyper-softs again and improves his time at the top of the pile with 1:19.854 before heading back in.

Lewis Hamilton then returns to the track and he has it to himself at the moment.

Speaking of Lewis Hamilton, he is finally out on track, popping out for an installation lap.

A busy afternoon ahead for the reigning world champion?

Richard Ellis: If Bottas had all day Tues in the car and there was limited running yesterday, why haven’t @MercedesAMGF1, external given @LewisHamilton, external more time in the car?

Pierre Gasly, on super-softs, moves up to third with 1:22.315.

Sebastian Vettel improves again, joining Stoffel Vandoorne in the 1:20s and he does a 1:20.824.

Both drivers head back to the pits leaving Pierre Gasly and Sergio Perez on the track.

The first of many wins to come?

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Sebastian Vettel inches closer to Stoffel Vandoorne's time as he improves with 1:21.256.

Vandoorne is back out, remaining on hypersofts, and he subsequently lowers the benchmark with 1:20.068.

Sebastian Vettel is up to second as he does a 1:22.087 on his 50th lap of the day. That puts him within 1.5 seconds of Stoffel Vandoorne's time, which came on the hyper-softs.

Liam: There can be no denying. That McLaren is looking promising, and not just in an aesthetic sense.