HBO has ordered a pilot episode for a potential Game of Thrones spinoff which would be a prequel to the main series.
The US network has announced it has commissioned a pilot for an untitled series written by Thrones author George RR Martin and British screenwriter Jane Goldman.
The prequel takes place thousands of years before the battles over the Iron Throne.
HBO said in a statement: "Taking place thousands of years before the events of Game of Thrones, the series chronicles the world's descent from the golden Age of Heroes into its darkest hour.
"And only one thing is for sure: from the horrifying secrets of Westeros's history to the true origin of the White Walkers, the mysteries of the East, to the Starks of legend … it's not the story we think we know."
No other details about the prequel series have yet been announced, but executives from the network say any spinoff will not be broadcast until after Game of Thrones' eighth and final season in 2019.
Jane Goldman is best known for her collaborations with filmmaker Matthew Vaughn on the screenplays of Kingsman: The Secret Service and its sequel Kingsman: The Golden Circle, and X-Men: First Class.
She also wrote Disney's upcoming remake of The Little Mermaid.
Production is currently underway on the final season of Game of Thrones which is due to air in 2019.
