Game of Thrones can’t have been an easy sell to the executives at HBO. George RR Martin’s sprawling series of novels may have been critically acclaimed but most fantasy TV is of the Xena: Warrior Princess or Merlin ilk. Fantasy is rarely taken seriously despite the anomaly of Peter Jackson’s Lord of the Rings. The budget for the first season has been estimated at $50-60 million, a massive investment for any company.

Now – after all the Emmys, Golden Globes and Hugo Awards – it doesn’t seem like such a crazy risk. They must have been confident that the Dungeons & Dragons crowd would tune in but they can’t have expected it to be such a hit beyond the geeks. ‘What is surprising is the range of people that have approached me,’ adds Michelle Fairley (who plays Lady Catelyn Stark). ‘I meet people I never imagined would be interested in this sort of genre, and I think that is testament to the series. I think the appeal is that it is totally about the characters, and the ordeals they find themselves in.’

It fell to showrunners David Benioff and DB Weiss to take the source material and adapt it for television. Benioff himself coined the phrase ‘The Sopranos in Middle-earth’ that was soon taken up by the world’s media. It was a perfect soundbite: Game of Thrones easily matches the acting and drama of David Chase’s mob story and the intricate detail of Tolkien’s magnum opus.

There may be a backdrop of swords and sorcery but Thrones is a character driven show. ‘That’s what George did so cleverly within the novels,’ explains Fairley. ‘He creates extremely real people who audiences can care about. They have the same dilemmas that we all have, like worrying about their families or just surviving in this world. These characters experience grief, war and loss, just like real people. It resonates because of that, irrespective of the setting. It’s good drama. It’s wonderful drama.’

Game of Thrones is set in a world split into various kingdoms constantly vying for supremacy, the two most powerful being the stoic Starks who are willing to stand up to the ruling Lannisters, now headed by the evil boy-King Joffrey (a cowardly tyrant played with real venom by the young Jack Gleeson). Even the villains are incredibly well written with rich back stories. ‘I like the Lannisters,’ says Nikolaj Coster-Waldau, who plays errant knight Jaime Lannister, who is Joffrey’s uncle/father (it’s complicated and very twisted). ‘There’s a brutal honesty about the family. I’m not sure about Joffrey. He has some issues …’

The show isn’t afraid to wrong foot you as the story dictates; for example (spoiler alert) Sean Bean was the obvious headline star but he had been executed by the end of the first season. While there is a particular focus on young actors in gritty roles and as this is cable TV expect blood, guts and death.

‘Before I began, David Benioff and Dan Weiss spoke to my parents and made them aware of the type of show I was joining,’ explains Maisie Williams (who was just 14 when she joined the show as feisty tomboy Arya Stark). ‘When you’re filming, it’s very different from what you see on screen. I saw how the [Bean] beheading scene in season one was created, and most of the time it was just a guy swinging a sword near his head. So, for me, it wasn’t that graphic at all.’

Though don’t be fooled: this isn’t a dialogue led production in a medieval setting; there are dragons, monsters and witches while the men of The Wall protect the kingdoms from the horrors beyond in The North.

With the Starks and Lannisters locked in bloody battle, we are poised to be thrown headlong into the action as Game of Thrones returns for a third series. ‘When I first read the script for season three I thought it was the best yet,’ says Fairley. ‘The stories are so layered, and the characters richly developed. Their dilemmas are even more pressured and the stakes even higher.’

Game of Thrones, season 3, premieres on Sky Atlantic HD, Mon 1 Apr, 9pm (seasons 1 and 2 will also be available On Demand).

Game Of Thrones Season 3: Trailer #2