A Game of Thrones spin-off sequel centred on Jon Snow is in early development at HBO, with actor Kit Harington set to return to his role if it goes ahead.

First confirmed by the Hollywood Reporter on Friday, the so far unnamed show will take place after the events of Game of Thrones, which ran for almost a decade between 2011 and 2019 and became one of the biggest television series of all time.

Set in the world of George RR Martin’s fantasy books, the new show is the first of the subsequently announced Game of Thrones spin-offs to be a sequel, and a sign HBO will extend Martin’s world beyond the source material, reopening what was previously thought to be the end of the saga.

Martin has yet to finish writing the books, with fans having waited 11 years so far for the sixth of seven books.

HBO’s adaptation ended with Snow, previously thought to be the bastard son of Ned Stark, realising that he could be an heir to the iron throne. In the final scenes, Snow went into exile from Westeros to begin a new life.

It is so far unconfirmed if the few familiar faces who were still living at the end of the notoriously grisly series – such as his half-siblings Arya Stark (Maisie Williams) and Sansa Stark (Sophie Turner) – could appear in the show.

HBO’s upcoming spin-off House of the Dragon, set 200 years before Game of Thrones, will start on 21 August. Other spin-offs previously confirmed by HBO include Tales of Dunk and Egg, 10,000 Ships and Nine Voyages, which are all prequels.

Harington was nominated for two Emmys for his performance as Snow.

HBO have declined to comment. Representatives for Harington did not immediately respond to request for comment.