Ahead of today's sole free practice session the air temperature is 18 degrees C, whilst the track temperature is 24 degrees. It is bright but there's lots of cloud

Lewis Hamilton was the pace-setter in both of Thursday's sessions, though track time in FP2 was compromised first by Roberto Merhi's crash and then the weather gods.

Consequently, there was no running on the option supersoft tyres - making its debut this weekend - unless you count Pastor Maldonado's extremely slippery reconnaissance effort.

Whilst Nico Rosberg and the Ferraris were 'up there', particularly in FP2, it was the form of the Toro Rosso duo - both driving here for the first time - that really impressed. Indeed, in FP1 Max Verstappen was second quickest, only 0.149s off Hamilton's pace. Sister team Red Bull was also quite... well, "bullish" about its chances here.

With the teams having to complete the work they should have done on Thursday, and get a taste of the option rubber, this morning should be quite busy.

As stated, the supersoft - which is an all-new compound - is making its 2015 debut, whilst There is just one DRS zone, and that's on the pit 'straight'.

Whilst Merhi's accident was on the exit to the tunnel heading in to the Nouvelle Chicane, it was Ste Devote and Mirabeau that witnessed the most incidents.

The lights go green and Ricciardo, who has been waiting patiently at the end of the pitlane for some time, heads out. He is followed by Sainz, Ericsson, Nasr, Verstappen and Raikkonen. Both Manors on track also, both on the option rubber... the Mercedes duo also of the supersofts.

Sainz gets things underway with a 23.987, but this is soon beaten by Verstappen and then Perez (21.129). Less than five minutes in and there are already ten names on the leaderboard.

Hamilton goes quickest (19.074) as Button is told that he has a new knee-pad. "Hopefully this will be better," says the engineer. Bet it isn't.

Kvyat goes second (20.128), ahead of Grosjean and Hulkenberg, as Rosberg posts 26.342.

Grosjean improves to second with a 19.487 as Hamilton ups the ante with a 17.504. Moments later Rosberg posts 18.356 to make it a Mercedes 1-2.

Kvyat complains of turbo lag.

A big lock-up for Grosjean at Mirabeau as Rosberg improves to 17.913.

After ten minutes all but the McLarens, Ferraris and Ricciardo have posted times.

Kvyat has to use the run-off after getting it wrong at Nouvelle Chicane.

Another improvement from Hamilton, the Briton stops the clock at 17.021. Next time around it's a 16.705 whilst teammate Rosberg posts 17.271.

"Keep pushing, keep pushing, tyres good for two more laps," Hamilton is told. "The tyres won't last two laps," he replies.

As Rosberg complains of; "too much oversteer in lower speeds, think I need to reduce engine braking", Raikkonen and Vettel are on track, on primes.

On the harder rubber Raikkonen goes third, 1.701s off Hamilton's best. Moments later teammate Vettel posts 18.636 to go fourth, only to be demoted by former teammate Ricciardo.

Next time around Raikkonen closes to within 1.387 of the world champion as Button (primes) goes seventh (18.812).

A big lock-up and a trip down the escape road at Nouvelle for Vettel whose helmet has been adapted to resemble that of (in our opinion) Arturo Merzario.

Twenty-five minutes in and drivers start to follow Mercedes lead and switch to the softer rubber... among them Raikkonen.

The Finn posts 17.401, still 0.696s off Hamilton's pace. Unfortunately, he won't be closing the gap any further, he hits the barriers at Ste Devote with the rear of the Ferrari. "I think I punctured the rear," he says.

The session is red flagged.

Current order, after thirty minutes, is: Hamilton, Rosberg, Raikkonen, Alonso, Hulkenberg, Maldonado, Button, Ricciardo, Vettel and Grosjean.

In no time at all the Ferrari has been pushed to safety and the session resumes... courtesy of some sterling work by the marshals.

Ferrari reports that Raikkonen's left-rear was punctured... however, that was the result of the accident, not the cause.

As most drivers now switch to the option rubber, the Mercedes duo, doing their own thing as ever, switch to primes.

Verstappen improves to fourth with a 17.788, the youngster looking like an old pro here.

A 16.885 sees Vettel improve to second, closing to within 0.180s of Hamilton who has gone straight on at the Nouvelle Chicane.

Oh dear, we've done a Murray Walker. Verstappen has hit the barrier at Anthony Noghes - the corner leading on to the pit straight. Hitting the barriers with the rear of the Toro Rosso, he damages the rear wing end plate. He is able to head back around the circuit to the pits but slowly.