Nearly eight years after the first movie extravaganza arrived in cinemas, the cameras have finally started rolling on James Cameron's long-awaited Avatar sequels. Four films are being made in total, continuing the story of Jake Sully, Neytiri and the world of Pandora.

Cameron's original sci-fi fable grossed $2.7 billion at the worldwide box office, making it the most successful movie of all time. Sequels were inevitable, but have taken an incredibly long time to make a reality.

Regular updates from Cameron were interspersed with delays, with Avatar 2 originally given a 2014 release date but now being set for 18 December 2020.

The budget of more than $1 billion being reported by Deadline is for all four films, making the budget of each roughly $250 million. The original itself cost studio 20th Century Fox slightly less to make.

Clearly that film turned a huge profit, and Fox are banking on that being the case in the 2020s despite the lengthy gap between the first film and its sequels.

Avatar was set on a distant, habitable moon called Pandora which humanity was mining of its resources with little regard for the native Na'vi population. As a means of exploring the world, which has an atmosphere toxic to humans, people inhabit genetically-engineered Na'vi bodies, called avatars, they inhabit and control with their brains from special pods.

Jake Sully (Sam Worthington) meets Neytiri (Zoe Saldana), and is introduced to Na'vi society. Eventually they wage a war against the increasingly hostile humans, save the day and then Jake decides to stay with the Na'vi permanently.

Worthington and Saldana are set to return, alongside Sigourney Weaver as Dr Grace Augustine (despite the death of her character in the first film) and Stephen Lang as the villainous Colonel Quaritch (despite the death of his character in the first film).

The one face confirmed so far is Fear The Walking Dead's Cliff Curtis. More names will be announced over the coming months.

Cameron began the film's shoot in Manhattan Beach, California, and is expected to film Avatar 2 and Avatar 3 simultaneously before a break to allow for post-production on those films set to release in 2020 and 2021.

The production of Avatar 4 and 5 will then start up again as those films target releases in 2024 and 2025. The release date of each film is around mid-December.