The new Formula One season begins in Bahrain on Sunday with Lewis Hamilton bidding to win an unprecedented eighth world championship.

Here, the PA news agency looks at a number of key questions heading into the 2021 campaign.

1. Is Hamilton the favourite to win another title?

Hamilton and Mercedes were at their imperious best last season, and with only minor tweaks to the regulations, many anticipated the British driver will waltz to his eighth world crown.

But the Silver Arrows endured a poor pre-season campaign. They ran into reliability issues, with both Hamilton and team-mate Valtteri Bottas complaining about the handling of the new car.

In contrast, Max Verstappen's Red Bull team enjoyed their best days of testing since they last won a world championship in 2013. Verstappen posted the fastest time of anyone following a trouble-free week.

2. So, could Verstappen take the fight to Hamilton?

Make no mistake, Mercedes departed the three-day test believing Red Bull have a quicker machine, leading to the prospect of a mouth-watering showdown between Hamilton and Verstappen.

Red Bull have been notorious slow-starters in recent years so their pre-season form will give them the belief they can challenge Mercedes who are on an unprecedented run of seven drivers' and constructors' titles.

Following the arrival of Sergio Perez from Racing Point – after the London-born Alexander Albon was dropped – they head into the new season with a stronger driver line-up, too.

3. Why did Hamilton sign only a 12-month extension?

Mercedes boss Toto Wolff claimed it was because they ran out of time to agree on a longer contract, while Hamilton said it leaves him free to take up other options – one of which, we have to assume, is retirement.

But the drawn-out negotiations, and Hamilton's subsequent demeanour, suggests all is not rosy in the Mercedes camp.

Commenting on the deal, the respected Sky pundit Martin Brundle said: "It is confusing. Lewis doesn't seem entirely happy with it."

4. Could this be his final campaign in the sport?

Yes. Hamilton is 37 next year and Mercedes are weighing up life after their superstar driver.

Verstappen is on Wolff's radar while the talented Briton, George Russell, a member of the Mercedes' academy, is desperately seeking a promotion from Williams following his brilliant stand-in performance for Hamilton at last year's Sakhir GP.

A proposed future salary cap for 2023 means Hamilton will also take a huge hit on the £40m-a-year he is currently earning on any future deals.

5. Who will lead the midfield fight?

Mercedes and Red Bull are set to be the front-runners with a number of teams jostling behind.

McLaren, who will be powered by Mercedes this season and fresh from finishing third in last year's constructors' championship – their best finish since Hamilton left at the end of 2012 – were pleased with their showing in testing.

Red Bull's sister team AlphaTauri also looked in good shape.

6. And what about the others?

Fernando Alonso is back on the grid this season following a two-year absence and the double world champion – despite suffering a fractured jaw in a cycling accident last month – didn't look out of place for Alpine, formerly Renault, in testing.

Sebastian Vettel has transferred to Aston Martin – the British team returning to the sport following six decades away – after he was dropped by Ferrari. But the four-time world champion ran into a number of mechanical hiccups at the test in Bahrain, recording the fewest laps of any driver.

Ferrari have already turned their attentions to next year, while Alfa Romeo, Williams and Haas are expected to bring up the rear.

7. Are there any fresh faces on the grid this year?

Yes, three. Mick Schumacher, the son of seven-time world champion, Michael, is the most high-profile of the trio. The presence of the 22-year-old, who won last year's Formula Two title, ensures the Schumacher name returns to the grid 30 years after Michael made his debut and nine since he retired.

Schumacher will be partnered by Russian, Nikita Mazepin, while Japanese driver Yuki Tsunoda has joined AlphaTauri. In all, only Mercedes, Alfa Romeo and Williams have retained the same driver line-up from 2020.

Of those not already mentioned, Daniel Ricciardo is now at McLaren alongside Lando Norris, with Carlos Sainz leaving the British team to replace Vettel at Ferrari.

8. What else do I need to know?

Formula One has a new CEO, former Ferrari boss Stefano Domenicali. He replaces Chase Carey following the American's four-year spell at the helm of the sport.

A record-breaking 23 races have been scheduled (Covid dependant) with Saudi Arabia set to host its first grand prix in December.

The two practice sessions on Friday have been reduced from 90 minutes to one hour, while the sport is also set to trial sprint races at three rounds this year – including the British Grand Prix.

A shorter race, approximately 30 minutes, will take place on Saturday, replacing qualifying, and determining the grid for Sunday's grand prix. Confirmation of the finalised sprint race plan is expected in Bahrain this weekend.