The Batman 2 writer teases two notebooks full of material for his Game of Thrones spin-off Aegon's Conquest

The Batman 2 screenwriter Mattson Tomlin is working hard on his Game of Thrones spin-off.

"Always satisfying to finish filling a notebook," he wrote on Twitter, alongside a photo of two notebooks. One is labelled "Conquest/Caine 24/25", while the other is marked "Conquest/Possessor/16 Bars/The Crew."

"Conquest" refers to Aegon's Conquest, which has been in development for around two years now. Originally assumed to be another TV show, last month it was reported that the project "is being developed by HBO as a possible drama series and by the Warner Bros. film team as a mammoth Dune-sized feature film."

Set 100 years before House of the Dragon and 200 years before Game of Thrones, the project will follow King Aegon I Targaryen as he conquered and united six of the seven kingdoms of Westeros (Dorne retained its independence for a while longer) and commenced centuries of Targaryen rule on the Iron Throne. He foresaw "the end of the world of men", caused by a long winter from the North (sound familiar?), which could only be defeated if a Targaryen ruled over Westeros – a prophecy that he called the 'Song of Ice and Fire'.

House of the Dragon season 3 is on the way later this year to continue the story of the Targaryen civil war that takes place a century after the Conquest, but, in the meantime, there's another Game of Thrones spin-off on our screens: A Knight of the Seven Kingdoms.

This show follows hedge knight Dunk and his young squire Egg as they seek fame and fortune at a tourney – but not without running into some trouble first. This is Westeros, after all.

A Knight of the Seven Kingdoms airs weekly on HBO/HBO Max and Sky Atlantic/NOW. Make sure you never miss an episode with our A Knight of the Seven Kingdoms release schedule, or check out our verdict in our A Knight of the Seven Kingdoms review.