Early days, but this morning's session has certainly whetted the appetite.

While Max Verstappen led a Red Bull 1-2, with Sebastian third quickest, it should be noted that the best time posted by the Mercedes duo, who finished fourth and fifth, was on soft as opposed to ultrasofts.

To add a little more spice, Rosberg crashed in the final stages of the session, taking off his front wing in an incident which has yet to be explained.

Behind the Red Bulls, Ferraris and Mercedes came the Toro Rosso duo, the Faenza outfit, celebrating its 200th Grand Prix this weekend, running Sainz and Kvyat in back-to-back tests, the Spaniard with the new aero package and his Russian teammate the old.

Williams continued its tradition of using Friday for practice, while Haas only had one car in action, Grosjean sidelined by an air intake issue.

Alonso, trying the Halo for the first time, was just outside the top ten, while teammate Button, who was able to continue despite an early technical glitch which left him stranded on track.

As ever, Force India is playing the long game, both drivers sticking to the soft tyre for the entire session.

Renault, Sauber and Manor were all well off the pace, all three reliant on Singapore producing a few of its usual surprises over the next couple of days.

Ahead of today's second session, which gets underway at 21:30 (local time), the air temperature is 29 degrees C, while the track temperature is 33 degrees.

The lights go green and Wehrlein leads the way, followed by Gutierrez and Ocon. Vettel is another early riser, as is Rosberg.

Wehrlein gets proceedings underway with a 51.707, but this is quickly beaten by Ocon and then Gutierrez (48.700).

Going purple in all three sectors, as you'd expect, Vettel posts 47.475 to go quickest, the German running wide in the final corner.

Moments later teammate Raikkonen posts 46.167 however, the Finn is on supersofts whilst Vettel was on the softs.

Button (supers) goes third but is instantly demoted when Rosberg (softs) posts 46.990.

The Toro Rosso duo are at it again, Kvyat goes second (46.909) to go second while Sainz goes third with a 46.924.

Alonso is the latest driver to kiss the barriers at T10, the damage to the advertising hoarding suggesting it was quite passionate.

Hamilton (supers) goes quickest in all three sectors to post 45.275, but Ricciardo is already on a hot lap. He loses a little pace in S2, finally crossing the line at 45.620 to take second, 0.345s down on the Briton.

"Track evolution is always a big factor here," confirms Pirelli, "so watch for the times getting quicker and quicker as session goes on."

Sainz has a moment at T10, but somehow manages to give the barrier the very lightest of touches. This corner, along with 21 and 22, is catching out a lot of drivers today.

Ricciardo spins at T11 but somehow keep it out of the barriers. Meanwhile, teammate Verstappen improves to third (46.028).

"Traction and braking are the key aspects here with 23 corners," says Pirelli. "So drivers must be careful not to overheat tyres: the ultrasoft especially."

Ocon is the first driver to try the ultras and it isn't long before he regrets the move, the Frenchman clouts the barrier at T19 then T21 for good measure.

"I hit two times the wall," admits the Manor driver. Asked if the car has been affected he replies: "No problem".

Despite Ocon's trials and tribulations, more and more drivers switch to the ultras.

Vettel, on the ultras, goes quickest in S1. He loses pace in S2, finally crossing the line at 45.266 to go quickest.

As Hamilton complains of a "lot of heat in the right hand side of the cockpit," Raikkonen looks set to improve. Sure enough, the Finn posts 44.427 to take the top spot but moments later Rosberg bangs in a 44.152.

Hamilton runs wide in T2, thereby ruining his lap.

On the ultras, Hulkenberg posts 45.182 to go fourth. Teammate Perez, who is still on softs, is currently eighth (46.444).

On the ultras Verstappen can only manage third (44.532).

As we await Ricciardo to try the ultras, Alonso is out on softs.

Nasr takes full advantage of the escape road at T14 after making mistake.

Talking of mistakes, Hamilton is having a nightmare having gone wide at a number of corners and thereby spoiling a number of laps.

Check out our Friday gallery from Singapore, here.