George R R Martin has signed a contract with HBO and four writers to prolong Game of Thrones with some spin-offs.

A spokeswoman for HBO said: "We'll take as much or as little time as the writers need and, as with all our development, we will evaluate what we have when the scripts are in."

One of the four writers up to extend the show is Jane Goldman, who co-wrote the superhero flick Kick-Ass.

Mad Men writer Carly Wray, Brian Helgeland (LA Confidential) and Max Borenstein (Kong: Skull Island) are the other three on board.

There's massive scope to explore other kingdoms within Westeros as well as giving main characters some in-depth development.

There is currently no set deadline for the spin-off shows.

Other big American shows have had successful spin-off shows such as Breaking Bad with Better Call Saul which has been received highly by viewers.