Force India:, external The main focus of today's work is to allow Nico to have an in-depth assessment of the new 2015 tyres, together with mileage.

And now Daniil Kvyat puts a time on the board, a 1:42.118 on his 24th lap before improving to 1:34.031.

Fernando Alonso is making up for lost time as he completes his sixth lap of the circuit. As it stands, Felipe Nasr and Daniil Kvyat are the only drivers still to record timed laps. Nasr is back in the Sauber garage as the team looks to resolve an issue that has hampered their running today, while Kvyat has been working through a programme of untimed runs, like he did yesterday morning.

John Gilmore:, external If McLaren turn up the power at end of test other teams will head to first race not knowing what the car is capable of - #mindgames.

There it is. Fernando Alonso, on medium tyres, gets off the mark with a 1:30.427, the seventh fastest of the morning so far, but immediately improves with 1:28.364.

Fernando Alonso is back out on the circuit and we could be about to see a first timed effort of the day from the McLaren.

Sebastian Vettel ends a brief moment of circuit silence, with everyone else back in the pits.

Image source, Toro Rosso

Toro Rosso:, external Sun is shining also from the Fastest Laps screen... Carlos Sainz is on top!

Finally, the sight McLaren fans, and the Spanish spectators in the stands, have been waiting to see - Fernando Alonso heads out in the McLaren and completes his first lap of the day.

Scott Ambrose:, external No surprise at McLaren's initial problems but do think that car will have plenty of pace and power - eventually.

Image source, McLaren

Former Barcelona president Joan Laporta has paid McLaren a visit this morning.

I don't know about you, but Fernando Alonso has the look of a man desperate to be anywhere else but there. Like, the circuit for example.

Not much to separate Sebastian Vettel, Nico Rosberg and Carlos Sainz at the top of the order, with Sainz reclaiming top spot as he clocks 1:27.236 on softs.

F1 journalist Dan Knutson in Barcelona: "Williams planned to do pit stop practice today and chassis set-up work yesterday, but with the patchy rain on Saturday the team switched things around so that the drivers could lap on a dry track today. Felipe Massa and Valtteri Bottas each did 20 pit stops yesterday, so the crew got a real workout."

Romain Grosjean has been making marginal improvements with each lap and is currently fourth fastest with a 1:28.029. Nico Rosberg is also improving as a 1:27.663 puts him just 0.013s off Sebastian Vettel. Both are on the medium tyre.

A reminder that the plan is for Fernando Alonso and Jenson Button is to share track time today, so neither will probably want these delays to go on much longer.

Andrew Benson
Chief F1 writer

"A McLaren spokeswoman says: 'The new part (MGU-K) arrived late last night so we needed time for the power unit reconfiguration. We should be on track very very soon.'"

Image source, Romain Grosjean

Lotus:, external 17 laps on the board, latest tweaks completed in the garage, Romain Grosjean returns trackwards.

Nico Rosberg dips below 1:30 for the first time today with a 1:28.216, before shaving off 0.041s to close in on Sebastian Vettel's best effort.

Nico Hulkenberg heads back out, as does Sebastian Vettel and the latter, on medium tyres, storms to the top of the timesheet with a 1:27.474.