Hamilton is clear favourite to win the 2018 F1 title says Nigel Mansell

World champion Lewis Hamilton must be considered as the overwhelming favourite to win his fifth Formula One title this season, according to Nigel Mansell.

Hamilton, 33, is due at Silverstone on Thursday as he and team-mate Valtteri Bottas unveil Mercedes' new car for the forthcoming campaign.

Mercedes have been the sport's dominant force in recent times with Hamilton surpassing Sir Jackie Stewart as the only British driver to win more than three championships after he beat Ferrari's Sebastian Vettel to the title last year.

Hamilton has kept a low profile over the winter break following criticism he courted after comments made about his nephew in a social media post at Christmas.

But the Englishman will make his first public outing of the new year on Thursday when he takes the wraps off the Mercedes that 1992 world champion Mansell believes could fire him to further glory.

"There is no question that Lewis and Mercedes are the clear favourites again," Mansell told Press Association Sport.

"Lewis has got many more years in him if he has got the appetite, and I can see no reason why he cannot win a few more world championships and set the bar very high for the future.

"I just hope for the good of Formula One that Ferrari, Red Bull and even McLaren can put a challenge to Mercedes so we can have some exciting racing.

"You mustn't underestimate the great job that Ferrari did last year - although they had problems and Sebastian had a few races that went the wrong way - without their tremendous strive to win the championship it wouldn't have been as exciting as it was.

"I hope they continued in that vein over the winter, and hopefully Red Bull have found some more power from their Renault engine, too."

Hamilton's contract expires at the end of the year, and while his Mercedes team are confident their star man will sign a new two-year deal, the lack of a formal announcement is likely to keep the sport's major players on their toes.

Both Kimi Raikkonen and Daniel Ricciardo have only this year to run on their respective deals at Ferrari and Red Bull, while McLaren chief Zak Brown recently admitted that he would be interested in offering Hamilton a second chapter with the British team.

"I would be very surprised if Lewis did not sign a new deal with Mercedes," Mansell added. "But if Red Bull or Ferrari were to do something special over the winter by making the jump over Mercedes, and then offer Lewis an incredible deal, who knows?

"At the moment however, Lewis has the world at his feet, he is in the best car and at the best team, so why would you want to change it?

"Some people in their careers are very privileged to be in a strong position and Lewis is one of those because he can afford to be patient. When the time is right for him, he will sign on the dotted line."

- Nigel Mansell was speaking after helping deliver a new £7million helicopter to the Midlands Air Ambulance Service, with public donations raised in just three years funding the new aircraft.