The Game of Thrones prequel casts Naomi Watts in a mysterious role - but fans think she's playing a Targaryen

The Game of Thrones prequel has finally added its first cast member. Even better: said member is only Naomi Watts, the Academy Award nominee who shot to fame in Mulholland Drive and has, more recently, starred in the revival of Twin Peaks and Birdman. She’s pretty much acting royalty at this point but, very soon, she could become fictional royalty – as fans think they have a good handle on who she’ll be playing.

Deadline has revealed that Naomi Watts will be joining the Game of Thrones prequel, but not as the sole female lead. Instead, HBO President of Programming Casey Bloys says: “There are very strong female characters but it’s an ensemble, there is men and women… There are a lot of very complicated leads.”

HBO, meanwhile, has described Watts’ role as being "a charismatic socialite hiding a dark secret." That, alongside the fact that Watts is blonde has led many fans to believe she’ll be playing a Targaryen, with some even going as far as saying it’ll be Rhaenyra Targaryen, the great-grandmother of Daenerys Targaryen.

At the risk of adding two plus two and getting… a blonde woman playing a Targaryen (it’s a bit too obvious, right?), it would certainly give the show a definitive link to Game of Thrones proper, which might be the best way to draw viewers in for the pilot.

However, it’s probably not going to be Rhaenyra. HBO has made it clear the Game of Thrones prequel is set thousands of years before the original show, while Rhaenyra was around only a few hundred years before the likes of Jon Snow and Daenerys, ahem, rocked the boat.

Still, this is a promising start – it’s not every day you can nab such an esteemed actress for a TV show – and it’s the sign of the frenzy around the franchise that even someone’s hair colour can set tongues wagging. Naomi Watts, your watch has begun.

Before that, there's the small matter of Game of Thrones season 8 and all the predictions and theories that come with it is just around the corner. Because you can never get enough Thrones.