Naomi Watts has admitted it is "intimidating" to be filming the Game of Thrones prequel due to the runaway popularity of the HBO fantasy series.

The Oscar-nominated actress was the first cast member to be confirmed for the project which will take place thousands of years before the events of the original series.

The new series comes from writer Jane Goodman, who wrote X-Men: First Class, and is overseen by GoT author R.R. Martin. It will explore the history of Westeros and the backstory of the White Walkers.

Watts who, plays a "charismatic socialite with a secret" in the highly-anticipated prequel which has already begun filming, has said it is "scary" to be part of the prequel but hopes Game of Thrones fans won't be disappointed.

Speaking to AP Entertainment, she said: "It is intimidating. It's very exciting, having just come off the last series, where the world was blowing up over it.

"Everything was Game of Thrones related. All the advertising on TV, every article - everyone's jumping on that bandwagon. So, it is scary."

She continued: "But hopefully, those fans come along and get to find something new and interesting in this world as well.

"I think they won't be let down, it’s a great team of people they’ve put together."

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