Ahead of today's opening session, the air temperature is 12 degrees C, while the track temperature is 18 degrees. It is somewhat cool, OK nippy even, and overcast, slightly foggy even.

Unlike Austin, there are no reserve drivers on duty this morning, while the cars of Perez, Massa, Wehrlein and Magnussen are all running the Halo device as testing continues.

The lights go green and the Gs get it underway, Grosjean and Gutierrez, they are followed by the Renault duo.

The circuit is very dusty and not at all grippy, as Wehrlein demonstrates as he runs wide.

Following its issue in Austin, indeed dating back to Bahrain, Haas is trying a new brake material.

In less than four minutes, everyone has been out, one of the last being Perez who gets a warm welcome from the crowd - if not the weather.

Sparks aplenty from Verstappen's car which appears to be running very low.

Vettel and Perez both report lots of dust.

Having completed the requisite installation lap all the drivers have headed back to the comfort, and warmth, of their garages.

After ten minutes of nothing, Ocon is the first driver to post a time, the Frenchman posting 1:28.842.

A big lock up for Alonso, who is switching between front wings this morning, the 'old' and a new one the team is trying. Nonetheless, the Spaniard posts a 26.398.

As Alonso improves to 25.933, Palmer and Button head out.

Alonso keeps chipping away, the Spaniard now down to 24.933.

"The main story so far is low grip," says Pirelli. "Just a question of running as much as possible to lay rubber down and generate as much heat as possible."

Running thus far has been on softs and mediums, however, Sainz, Kvyat and Hulkenberg are on supers.

Bottas goes quickest with a 24.337, ahead of Vettel (24.896), Alonso and Sainz.

It's business as usual as Rosberg posts 22.748 and Hamilton, who loses time in S2, 23.802.

Hulkenberg reports an issue with his DRS claiming that he cannot activate it anywhere, he is told to use it only where it is allowed.

Hamilton improves to 21.936 and his teammate 22.395.

Verstappen goes third (22.877), ahead of his teammate, but is demoted when Bottas improves to 22.837.

Perez delights the crowd when he posts 22.570 to go third, Gutierrez, currently 18th, doesn't appear to be stirring similar support.

The session is red flagged when Nasr loses part of his front wing after running over a kerb. Still running the Halo, the Brazilian is blissfully unaware. "Is something wrong," he asks "Is the car OK, I heard a strange noise."

While the replay shows him running wide, his front wing doesn't appear to hit the kerb.

Marshals take to the track to clear the debris.

"There's quite a mess on track," Ricciardo is told, "Nasr's front wing just exploded, basically."

As drivers are told that they may use their spare set of tyres for another seven minutes, Pirelli reveals: "So far, only five drivers have tried supersoft, Perez fastest of them."

At 10:42 the session resumes.

Verstappen's car is pushed into its garage, the left-rear brake smoking heavily. Even a blast from a fire extinguisher doesn't appear to help.

Wehrlein is the only driver yet to post a time.

Close up of Verstappen's car shows some burning damage around the brake drum to the carbon fibre. Indeed, this could be the end of the youngster's session. Indeed, the damage is to the rear brakes on both sides.

Around half-time, it's: Hamilton, Rosberg, Bottas, Masa, Verstappen, Raikkonen, Ricciardo, Vettel and Sainz.

Check out our Friday gallery from Mexico City, here.