Avatar: The Way of Water world premiere takes place in London

Kate Winslet, who first worked with director James Cameron on Titanic, appears in Avatar: The Way of Water

Avatar: The Way of Water, the sequel to the highest-grossing movie of all time, has held its world premiere in London.

Its much-delayed launch comes 13 years after the original sci-fi film, which was released in 2009.

Director James Cameron was joined on the blue carpet in Leicester Square by stars Sam Worthington, Zoe Saldaña, Sigourney Weaver and Kate Winslet.

The Avatar series is set on the lush planet of Pandora where the existence of the Na'vi people is under threat.

Speaking at the premiere, Weaver said the film has the "family" as the central theme over the environment as it is more "universal and relatable".

"It was a joy to be part of that family, we were at each other's throats sometimes, Jim [Cameron] wanted that... for us to kind of get at each other, still have fun and it's very much a real family," she said.

Here are some pictures from Tuesday's world premiere in London, and you can find more information about the film further down.

Actress Zoe Saldaña, who also starred in the original film, reprises her role in Avatar: The Way of Water

Actor Sam Worthington, pictured with wife Laura, also returns to the franchise for the Avatar sequel

Director James Cameron, pictures with his wife Suzy Amis, plans a further three sequels after this one

Actress Sigourney Weaver was also among the stars seen at the film's world premiere in London's Leicester Square

Actress Bailey Bass has joined the cast to play Tsireya, a young Na'vi from the Metkayina clan

Other stars seen on the blue carpet included Black Eyed Peas frontman will.i.am

The famous faces also included Star Wars actor John Boyega

Model Jourdan Dunn was also seen posing for photographers ahead of the film's premiere

Here are the answers to some burning questions earthlings may have about Avatar: The Way of Water.

What's the story?

The character Jake Sully (Worthington) seen with one of his children

The first film followed a paralysed marine Jake Sully (played by Worthington) as he travelled to the planet of Pandora, where he took on an avatar body.

He ended up joining the planet's indigenous population in fighting an attempt by humans to destroy their home to obtain a precious mineral.

The Way of Water is set many years later. Jake now has a family with Neytiri (Saldaña), and it follows their new life on Pandora.

When was it originally due to be released?

In 2010, a year after the original Avatar, 20th Century Fox (as the company was then called, before it was sold to Disney) said there would be two sequels, and that the first of those would be released in December 2014.

That target proved to be somewhat ambitious. And for the next few years, a regular story out of Hollywood was that the release date had yet again slipped back.

December 2014 became December 2016. Which became December 2017. Which became December 2018. You get the idea. Anyway, it's finally out next week, Friday 16 December 2022.

Why has it taken so long?

Much of the film takes place in the oceans of planet Pandora

Cameron threw out one version of an Avatar sequel that, after writing it, he decided didn't deliver.

The Canadian filmmaker also has a life outside cinema, and has spent some time doing deep ocean exploration (although maybe that counts as research for the new film, much of which takes place in and under water).

Cameron also wanted to plot out four sequels. And to take full advantage of new filming developments in the worlds of motion capture and CGI.

How long is it?

Well, it's not Cameron's longest film. That honour goes to Titanic, which clocks in at a hefty 3hrs 15mins.

But Avatar: The Way of Water isn't too far behind. Avatar 2, as it may otherwise be called, has a running time of approximately 3hrs and 12mins.

Slightly less if you dive out at the start of the lengthy end credits!

Who's in it?

L-R: Kate Winslet, Sigourney Weaver, James Cameron, Zoe Saldana and Sam Worthington at the London premiere

The stars of the original epic, Sam Worthington and Zoe Saldaña have returned.

So does Sigourney Weaver who - (spoiler alert) - died in the original film.

They are joined by young newcomers Jack Champion, James Flatters, and Trinity Jo-Li Bliss, alongside Oscar winner Kate Winslet.

What have the cast said?

Speaking about the sequel's storyline on Tuesday, Saldana said: "It felt like a natural progression for someone like Jake and Neytiri.

"That's the natural course that they decided to follow, is to start a family and and to keep that family together, to protect that family."

Director James Cameron said his own dreams inspired the film's dreamlike landscapes

Earlier in the evening, Cameron confirmed on The One Show he found inspiration from his dreams. "I just think the dreams are my own private streaming service that runs every night for free," he joked.

"I guess I do a lot of work in my dreams and I see a lot of imagery, sometimes [I] get up and write it down sometimes. With some of the stuff for Avatar when I was in college, I jumped up and did paintings... so this has been going on for a while."

He added: "I've always had dreams of being underwater with amazing animals swimming around and that sort of thing, so it's just kind of working all that subconscious imagery out."

How much money did the original make?

It's made a total of $2.92bn (£2.39bn) at the global box office, and is the biggest film of all time (unadjusted for inflation).

It briefly lost its title to Avengers: Endgame in 2019, but regained it after Avatar was re-released.

The original Avatar film is the biggest movie of all time

Will I need 3D glasses to see it?

The film is being released in a variety of formats. Including 3D, 2D and Imax. So no one's forcing you to see it in 3D if you don't want to.

But perceived wisdom is that a big part of the original's appeal was its stunningly immersive 3D sequences.

How many more sequels are planned?

Currently a total of four sequels are planned, including this one.

Avatar 2 is out next week, of course, while Avatar 3 has already been shot, and is due for release in 2024.

Avatar 4 has been partly shot ahead of a planned 2026 release. And Avatar 5 has a finished script. If it's made, and there is a question mark over that, it'll be out in 2028.

The uncertainty is because of the films' cost. The Way of Water had a budget of more than $350m (£287m) which means it needs to be hugely successful at the box office to recoup its money.

If it's a relative failure, it's hard to see Disney putting up hundreds of millions more to finish a series that they think the viewing public may have lost interest in.

Kate Winslet plays a character called Ronal

Do the sequels have names yet?

In 2018, BBC News revealed that the planned titles were The Way of Water, The Seed Bearer, The Tulkun Rider and The Quest for Eywa.

The Way of Water was finally confirmed in April of this year. Only James Cameron knows whether he will stick with the other titles.

What are The Way of Water's chances at the Oscars?

The original was nominated for nine Oscars including best picture, losing out to The Hurt Locker.

Its wins included best production design and best visual effects. Many expect that a similar showing is possible at the 2023 Academy Awards.