HBO has announced plans for four different spin-offs of hit TV show Game Of Thrones.

Author George R R Martin has signed a contract with the broadcasters and four "very talented writers" to prolong the network's most profitable ever show.

"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," a spokeswoman for HBO said on Thursday.

The network has not set a deadline for the projects.

One of the four writers hired to extend the show's success is Britain's Jane Goldman, who co-wrote the R-rated superhero flick Kick-Ass in 2010.


The other three are Mad Men writer Carly Wray, Brian Helgeland, who penned the crime caper LA Confidential, and Max Borenstein from Kong: Skull Island.

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The announcement comes as the series is gearing up for its inevitable end, scheduled for 2018.

It is a smart and predictable move for HBO, but one which has had varying degrees of success for other much-loved series.

While Cheers spin-off Frasier undoubtedly managed to emulate and even surpass the success of its predecessor, and Breaking Bad follow-up Better Call Saul has also been well received by fans, many have failed to stand on their own.

Image: Better Call Saul is one of modern TV's most successful spin-offs

Out of Friends, one of the most successful comedies in the US, came Matt LeBlanc's half-baked stand-alone, Joey.

From Happy Days came Joanie Loves Chachi, while MASH was followed by AfterMASH.

The list goes on.

By announcing four different Game of Thrones spin-off shows, HBO increases its probability of success, while officially turning a "vast and rich universe" into a full-blown franchise.

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It also gives room to try out several different types of spin-off, based around a stand-alone character, for example, or a side story or a character's origins.

In his book series A Song Of ice And Fire, Martin has created a world of his own, with different kingdoms, legacies and backgrounds.

Characters such as Tyrion Lannister and Jon Snow are good bets for stand-alone - if either manages to survive the cruel axe of Martin's pen.

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As for side stories, Westeros has seven different kingdoms, most of of which could easily stand on their own.

"The most natural follow-up would be an adaptation of my Dunk & Egg stories," Martin told Entertainment Weekly last year.

"There are eight million stories in Westeros and even more in Essos and the lands beyond. A whole world full of stories, waiting to be told, if indeed HBO is interested."

HBO is interested - but for now, fans can watch the seventh and penultimate series on Sky Atlantic, starting at 2am on 17 July.