Lost stars reveal truth about show's series finale 20 years on

It was the show that kept viewers glued to their television screens week after week as the survivors of Oceanic flight 815 fought for survival after crash landing on a mysterious, supernatural island.

Often revered as one of the greatest science fiction shows of all time, Lost had an ensemble cast of more than 20 main characters and a series of complex storylines including smoke monsters, time travel and a mysterious group of island inhabitants known as The Others.

But while many fans are still up in the air over exactly what was happening on the show or how it actually ended, 20 years on the cast have revealed what actually happened.

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"Not even the writers knew where they were going at the end of the last season and I think that we were kept in the dark for a reason, because they really didn't want to admit that they had no idea what was going on," original cast member Evangeline Lilly told Today Extra.

"I know that when JJ Abrams started the show, he wanted a box and he wanted the box to have something in it that was a mystery and they kind of went from there."

But Evangeline said the writers took a stand in season three and said they couldn't "indefinitely make excellent television" if it was going to go on forever and ever and they didn't know what the arc was going to be, because they don't know when and how it's going to end.

"So in season three, they made a really dedicated decision to end it after six seasons and from that point onward we were aiming towards a very specific arc, whether or not they knew exactly where that arc would drop, I don't know, I certainly didn't."

A lot of viewers still don't know what was happening - was the mysterious island actually purgatory and the "surviving" plane passengers were actually dead the entire series?

What was the evil Ben's true motivation on the island and what exactly was the black smoke monster?

But like Evangeline, Elizabeth Kelly, who joined in season three as one of the mysterious Others, said she also isn't too sure how it all ended.

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"I don't know, I always kind of liked it, I felt like I'm okay with the island being magic, I realise it's controversial, but I really quite loved it," she said.

But as popular as the series was and still is with fans, Evangeline, Elizabeth and co-star Malcolm David Kelly all revealed to Today Extra none of them have actually watched all six seasons of Lost - before hosts DC and Sylvia challenged them to a game of trivia on the show's plot lines.

"I'm going to stink at this game," Evangeline admitted.

Hear Today Extra's full chat with Evangeline, Elizabeth and Malcolm in thee video above