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20th Century Fox

James Cameron only ever goes bigger.

Titanic was a monumental task for any filmmaker and he followed that up with Avatar, a film of similar scope made more difficult by the use of 3D camera technology Cameron himself developed.

Avatar became the biggest film of all time in late 2009, so sequels were inevitable and Cameron was the only man for the job. Not content with keeping things (relatively) easy however, he decided not to make just one sequel, or even two, but three – and he's going to shoot them all at the same time.

"We wanted to shoot them together so we couldn't start one until all three scripts were done and approved," the Oscar-winner said at the Hero Complex Film Festival in Los Angeles (via Collider).

"I knew I was going to have to 'parallel process', which meant I would have to work with other writers," he continued."

"So we put together a team, three teams actually - one for each script. The teams consist of me and another writer on each one of those three films. Each would have their own script that they're responsible for.

"What we did that was unique beforehand was we sat in a writing room for five months, eight hours a day and we worked out every beat of the story across all three films so it all connects as one three film saga."

The writers are Josh Friedman (working on Avatar 2), husband and wife Rick Jaffa and Amanda Silver (Avatar 3) and Shane Salerno (Avatar 4). Friedman is best known for TV series Terminator: The Sarah Connor Chronicles, Jaffa and Silver made their name writing Rise and Dawn of the Planet of the Apes and Salerno wrote Michael Bay disaster flick Armageddon.

"I didn't tell [the three writers] which sequel was going to be theirs to write until the very last day. So everybody was equally invested story-wise in all three films. So the guy that got the third movie, which is the middle film of this new trilogy, he now knows what preceded and what follows out of what he's writing at any given moment.

"We all consider that to be a really exciting, creative and ground-breaking experiment in screenwriting. It worked as a process to get our minds around this epic and all these new creatures and environments and characters."

Avatar 2 is expected in December 2016, with sequels to follow in 2017 and 2018.