It was mixed fortunes for Mercedes in this morning's session, Nico Rosberg topping the timesheets whilst teammate Lewis Hamilton suffered an engine issue which has kept his team busy ever since.

"Investigations during the break have revealed a failure on the Power Unit inlet system of Hamilton's car," revealed Mercedes before the start of the session. "This does not affect his PU allocation for the season. Crew working hard to get him back out before the end of FP2."

With Williams maintaining its policy of not going for times on Fridays, it is unclear whether the Grove outfit is making progress relative to its German rivals however, no such problems for Ferrari, the Maranello outfit finishing second and third. Indeed, a late charge saw Kimi Raikkonen close to within 0.373s of Rosberg.

Romain Grosjean was a surprising fourth quickest, while both Toro Rossos made it into the top seven, once again seeming to have made a better job of it than its sister team.

The main talking point was the return of Fernando Alonso, the Spaniard completing 19 laps on his way to posting the fourteenth best time, three places ahead of his teammate.

This morning also marked the 2015 debut of Manor, both drivers over 6.5s off the pace and completing just 16 laps between them.

Early days, but the Force India duo also appear worryingly off the pace.

Tyres available this weekend are the hard (prime) and medium (option). There are two DRS zones, one on the start/finish straight and the other on the final straight.

As we await the green light, the air temperature is 32 degrees C, while the track temperature is 59 degrees C. Although it is currently bright and sunny, there is a chance of rain.

The cameras pick up on Alonso paying a visit to the Ferrari pit-wall, where he shakes hands with former teammates.

The lights go green and Stevens, waiting at the end of the pitlane performs a practice start as he is the first to take to the track.

As the Manor driver begins a flying lap, he is joined by Raikkonen and Kvyat.

The Briton posts 1:46.705.

"Very poor traction and exit in the last corner and turn two," complains Raikkonen as he begins his first flying lap. He subsequently posts 53.853.

Next time around Raikkonen improves to a far more sensible 41.002 but it isn't enough to beat teammate Vettel who has just posted 40.980 to go quickest.

Sainz goes third with a 42.671 ahead of Grosjean, Hulkenberg and Stevens.

As Maldonado sheds a piece of carbon fibre on the back straight, Ricciardo improves to third with a 41.789. The cameras pick up on Maldonado's Lotus whose left-side sidepod is askew possibly due to a pressure problem.

Nasr is on track, the Brazilian having handed his car over to reserve driver Marciello this morning.

As Grosjean runs wide in T1, Verstappen improves to third with a 41.765.

Bottas and Masa go third and fourth as Rosberg begins his first flying lap of the afternoon.

No messing, as Rosberg shoots straight to the top of the timesheets with a 40.438, 0.214s quicker than Vettel's best.

Just twenty minutes into the session, all but Kvyat, Hamilton and Merhi have posted times.

Button reports that gear change from first to second is "very poor".

Merhi posts 58.382 before improving to 54.849. His teammate is currently on 46.705.

On the half hour, Mercedes reveals that Hamilton is "suited and booted".

Out come the yellow flags as Merhi goes off and is stuck in the gravel at T11. Indeed, the session is red flagged as the Manor is stranded just yards from the edge of the track.

"I did a spin in the corner," says the Spaniard. "Yes, we can see that," is the weary response.

At this point, it's: Rosberg, Vettel, Raikkonen, Bottas, Massa, Verstappen, Ricciardo, Ericsson, Sainz and Grosjean.