The new Formula One campaign gets under way a week on Sunday when Melbourne’s Albert Park plays host to the season-opening Australian Grand Prix.

Lewis Hamilton will be bidding to defend his championship, but the Briton will have Ferrari’s Sebastian Vettel and Red Bull driver Max Verstappen hot on his heels.

Here, Press Association Sport takes a look at the key questions ahead of the 2018 campaign.

So, what did we learn from pre-season testing?

Mercedes appear as strong as ever, Red Bull and Ferrari are pushing to make it a three-way fight, while McLaren are facing up to another winter crisis. First, let’s start with the world champions. Lewis Hamilton’s Mercedes are bidding to win a fifth consecutive constructors’ title this year and they appeared in imperious form over the two weeks of testing in Barcelona. While Vettel posted the fastest time of the fortnight, Mercedes showed off their ever-impressive reliability – indeed they were the only team to break the 1,000-lap barrier – and looked the bees knees during race-style simulations, too. Red Bull appear to have made a step forward, but whether it will be good enough to challenge Mercedes remains to be seen. And although Ferrari caught the eye with Vettel’s unofficial track record of Barcelona’s Circuit de Catalunya, they did not appear to match Mercedes over their long runs. For McLaren, they enjoyed only two reliability-free days and will head to Melbourne firmly on the back foot.

Is the smart money on Hamilton to win another title then?

The bookmakers are in agreement that Hamilton is the favourite to join only Juan Manuel Fangio and Michael Schumacher as the third driver to win the Formula One title more than four times. Hamilton also stated ominously that this year’s Mercedes is an improvement on the one which fired him to a fourth title with two rounds to spare. Question marks had been raised over Hamilton’s mental state after a curious social media purge following comments he made about his nephew wearing a dress in an Instagram post at Christmas. But the 33-year-old was quick to bat away any negativity at Mercedes’ car launch at Silverstone and hailed “the longest break of my career” as putting him in the right frame of mind to execute a fourth title triumph in five years.

Who can take the challenge to Hamilton?

Vettel was Hamilton’s closest competitor last term, and but for a collapse in the second half of the season, he probably should have taken the Briton to the wire. Vettel and his Ferrari team will have learned lessons from their failures. Red Bull have not challenged for the championship since Vettel triumphed back in 2013, but Mercedes expect the team from Milton Keynes to make it a three-way fight, and in Max Verstappen and Daniel Ricciardo they possess arguably the best driver line-up on the grid. Hamilton’s team-mate Valtteri Bottas will also be looking to provide a sterner fight this season after a so-so opening year at Mercedes.

And what about McLaren… is it a make-or-break year for them?

The move from Honda to Renault power was supposed to usher in a new dawn for McLaren, but the British team are in choppy waters with the new season just around the corner. A faulty wheel nut inside the opening hour of the first day of the first test set the tone for a pre-season campaign which was severely hampered by reliability issues. Alonso and team-mate Stoffel Vandoorne lost valuable track time following a series of car failures and the Working marque completed just 599 laps, which was the fewest recorded by any team. Alonso provided some hope when he set the third fastest time of the winter in the closing minutes of the final test, but make no mistake, McLaren are under serious pressure, and cannot afford to repeat the misery of the last three years.

Are the cars any different this year?

A halo device fitted to a Red Bul car
(Tim Goode/PA)

The biggest change to the appearance of the cars is the introduction of the halo after the controversial cockpit protection device became mandatory for 2018. The halo, which Hamilton once described as the “worst looking modification in F1 history”, is in place to protect the drivers from flying debris and comes to fruition following years of research. The three-pronged device is made out of titanium and weighs seven kilograms. Remarkably it can withstand 12 tonnes of pressure, which is the equivalent of a double decker bus, and crucially, the driver’s visibility is not affected. Aesthetically, the halo is not pleasing on the eye, and it could be argued that it goes against the very principles of F1 being an open-cockpit series. Yet by the end of eight days of testing in Barcelona, it was no longer a talking point, and whether it is liked or not by the sport’s fans, it is here to stay.

And what are the other changes I need to know about?

The ugly T-wings and shark fins have been banned for 2018, while drivers will be allowed three engines for the year, rather than four. Meanwhile, F1’s overly-complicated tyre system has become even harder to follow following the introduction of two new dry-runner compounds, the ‘superhard’, and the ‘hypersoft’. There will be a record-equalling 21 grands prix in 2018 with the return of the French Grand Prix at Paul Ricard and the German Grand Prix at Hockenheim. There will be no Malaysian Grand Prix for the first time in two decades. European races will also start one hour later, in the hope of drawing in a bigger audience, while the lights will now go out at 10 past, instead of on the hour, to appease some television broadcasters. Oh, and grid girls are no longer. They will be replaced by grid kids.