Meanwhile it is all quiet on the circuit with everyone back in the pits.

Nico Rosberg has the benchmark time with 1:29.557, with the Ferraris of Sebastian Vettel and Kimi Raikkonen second and third fastest with 1:31.510 and 1:31.557 respectively.

So no Saubers any time soon then, and it looks like we won't be seeing anything of Manor in this session either. Here is Will Stevens watching his team work on his car.

Lee McKenzie
BBC F1 pit-lane reporter

"From the very start of this session both Sauber drivers were sitting in their cars, there are no wheels on the cars, there is nobody standing around, there is nothing happening at all and it is almost like the two drivers are two scared to get out of the cars, just in case something does happen."

Still no sign of the Saubers and it is looking unlikely we will see them any time soon, with Marcus Ericsson and Felipe Nasr both sitting in their cars in the garage, pretty much twiddling their thumbs.

I've not seen any confirmation on whether or not Giedo van der Garde will race this weekend, but it looks like it will be Ericsson and Nasr taking part in practice, if they do head out in this session.

Allan McNish
BBC Radio 5 live analyst

"Ferrari can challenge more consistently than in previous years but I don't think they will be challenging for a world championship."

We might see a rare smile on the face of Kimi Raikkonen this season after some impressive work in testing for Ferrari. He has just gone second fastest with 1:31.773s, just over two seconds off Nico Rosberg's pacesetting time.

Image source, Romain Grosjean

Following the helicopter crash in Argentina on Monday that killed eight French nationals, including three well-known French sports personalities, Lotus driver Romain Grosjean will wear a special helmet this weekend in tribute to those who lost their lives.

"I'll be wearing a black strip on my helmet at the Australian Grand Prix," he tweeted., external

Sparks flying from under Romain Grosjean's Lotus as he throws the car around the Albert Park circuit before Max Verstappen runs a little wide at a corner, but no drama.

Still just the two Mercedes with times on the board in these very early stages of practice.

Matthew Bruce: "Do I go to sleep or stay up and listen to the F1? I reckon Mercedes will still be on top maybe even further ahead than last year!"

I think we both know the answer to that one Matthew, pop the kettle on and power on through!

Lewis Hamilton is next to complete a timed lap with 1:32.044s, before his Mercedes team-mate Nico Rosberg improves with a 1:29.557.

Image source, Getty Images

The Mercedes are out and Nico Rosberg is first to pop a laptime on the board with a 1:31.319s.

Rosberg was all smiles in the paddock before the start of practice, donning a red nose for Red Nose Day, but he is very serious about his ambition for 2015. He is determined to beat Hamilton to the title.

James Allen
BBC Radio 5 live commentator

"Question marks over whether Manor F1 can run, due to software. Cars have been scrutineered though, so they are part of the meeting."

Image source, Manor F1

It is fantastic to see Manor in Australia, having only been cleared to compete at the opening race of the season last week.

The team, who competed as Marussia last season, came out of administration last month, and are set to race in Melbourne with a modified version of their 2014 car.

Plenty of hard work has gone into getting them at the race, but there might well be another bump in the road...

Manor F1:, external The first FP1 of '15 is underway. We've experienced a few hurdles to get here so we're not expecting our first morning to be plain sailing.

Image source, Getty Images

Whatever happens in the next 90 minutes, we certainly won't be in for a repeat of last year's first practice in Australia.

On that occasion, Fernando Alonso set the pace with a time of 1:31.840 in the Ferrari. His team-mate at McLaren this season, Jenson Button, was second fastest.

After a torrid time in testing, how McLaren would love to be in a similar position by the end of first practice in Melbourne this year.

Kevin Magnussen takes the McLaren out on to the circuit and 10 of the 20 cars have ventured out six minutes into this session.

Image source, Mercedes

Mercedes:, external That beautiful sound... that beautiful smell... we're all fired up & ready to rock.

The green light is on and the very first practice session of the 2015 season is under way!

Max Verstappen, the 17-year-old Toro Rosso driver, leads out the first few cars on to the circuit.

As mentioned earlier, Fernando Alonso is not in Melbourne as he recovers from his pre-season testing crash. Kevin Magnussen is stepping in for him this weekend, with Alonso hoping to be back in the McLaren for Malaysia.

"Of course, I'm very disappointed not to be joining Jenson in Melbourne in the McLaren-Honda garage, but I understand the recommendations of the doctors and I'm already back in training and preparing for my first race in the MP4-30," he said.

"Even though we faced a lot of challenges in the tests, I am very encouraged by the feeling I got from the car, and I'm looking forward to going through all of the data from this weekend with the team to continue our push for development and improve our performance."

Image source, Getty Images

Giedo van der Garde is certainly preparing to race. He is at the circuit today and is decked out in Sauber overalls.