Game of Thrones season 6: Ian McShane cast in 'mysterious' role rumoured to be Euron Greyjoy or Randyll Tarly

The actor is one of the biggest names to grace the HBO show

Actor Ian McShane attends the 64th Cannes Film Festival (Getty)

Speculation over season 6 of Game of Thrones is currently peaking: filming is currently going on in Northern Island and Jon Snow rumours are running rampant.

Emmy nominated actor Ian McShane is now joining the cast in a “mysterious role” according to Entertainment Weekly, and everyone is trying to guess who he will play.

Production won’t give away many details but apparently he won’t have much screen time but will be of “key importance”. So who could he be playing?

The first character to be speculated is Euron Greyjoy, the eldest of Lord Balon Greyjoy’s younger brothers, and a key character in the novels.

Unlike in George RR Martin’s books, the Greyjoy’s have yet to play any significant role so it would make sense for him to join now, especially if HBO are expanding to a minimum of eight seasons as previously reported.

Theon Greyjoy (Alfie Allen) on The Iron Islands

While there’s a strong case being put forward for Greyjoy, others believe he may be set to play Sam Tarly’s father, Randyll.

Again, a character neglected in the TV show, Randyll is originally a banner-man for Renly Tyrell but ends up supporting the Lannisters and is put onto Tommen’s small council by his uncle, Kevan Lannister.

Sam Tarly attempts to rally the men of the Night's Watch (HBO)

McShane is one of the biggest names to ever grace the show, as HBO have mainly chosen unknown actors for major roles – minus Sean Bean in season one.

The English actor is best known for his roles in the BBC’s Lovejoy, HBO’s Deadwood and a role in Pirates of the Carirrean: On Stranger Tides.