On Monday, Feb. 4, HBO programming president Casey Bloys told Entertainment Weekly that the as-yet-untitled project will begin production in early summer, following rumors that production would begin last fall and this February.
The prequel will star Naomi Watts, Naomi Ackie, Denise Gough, Jamie Campbell Bower, Georgie Henley, Sheila Atim and Alex Sharp and will be directed by SJ Clarkson. Showrunner Jane Goldman worked with Game of Thrones author George R.R. Martin to develop a concept for the show and a writers room is reportedly at work penning more episodes should they be ordered.
Bloys previously stated that the prequel will not premiere until at least one year after Game of Thrones concludes, which puts the series at a potential 2020 or 2021 start date. A filming location has not been confirmed, though it's thought that Game of Thrones' home base in Belfast, Northern Ireland will be utilized.
The show is rumored to be called The Long Night and will take place well ahead of the plot of Game of Thrones.
"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," the show's official description reads. "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."
Martin echoed the description while previously speaking to EW, explaining that the prequel will be very different from the show fans know and love
"Westeros is a very different place" he said. "There's no King's Landing. There's no Iron Throne. There are no Targaryens — Valyria has hardly begun to rise yet with its dragons and the great empire that it built. We're dealing with a different and older world and hopefully that will be part of the fun of the series."
HBO had initially announced the development of four Game of Thrones spinoffs in 2017, with a fifth project later revealed. According to Martin, one of those five projects is no longer active and all of them take place before the events of Game of Thrones.
Game of Thrones returns to HBO on April 14.
Photo Credit: HBO