The wait is over: Game of Thrones returns to our screens

We talk to the stars of Game of Thrones to get the lowdown on what we can expect from an action-packed season four of the HBO drama.

Sophie Turner as Sansa Stark and Peter Dinklage as Tyrion Lannister

It’s time to sharpen your sword and strap on your armour: Game of Thrones is back. Judging by recent activity, the fantasy show based on George R R Martin’s book series, A Song of Ice and Fire, returns with anticipation – to put it mildly – at fever pitch. In New York, 7,000 fans, many of them in costume, turned up in Brooklyn for a special fan premiere of Two Swords, the first episode of season four of the HBO show.

“It’s one of the biggest TV series in the world now,” remarks the Irish actor Aidan Gillen, who plays the scheming Littlefinger, one of a countless number of characters that populate Martin’s fictitious land of Westeros. When season three’s finale debuted, it was named 2013’s most pirated show by episode (5.9 million downloads, according to the website TorrentFreak) for the second year in a row – beating even the last-ever episode of Breaking Bad.

But what’s driving audiences wild? “It’s predictably unpredictable,” answers the young British actor Thomas Brodie-Sangster, who plays the seer-like Jojen. “Your favourite characters get killed off and you don’t know what’s going to happen.” Witness last season’s Red Wedding scene, in the penultimate episode, as several major characters from the Stark family – one of several clans vying for absolute power in Westeros – were massacred.

Cut to Twitter meltdown and fans posting their reactions to the scene on YouTube. “The passion and the horror – it was so much fun to watch,” says the Danish actor Nikolaj Coster-Waldau, who plays Jaime Lannister, the so-called Kingslayer. “But it shows that the audience is really invested in these characters.”

All the cast are regularly besieged by fans. “A guy put a curse on me in Poland!” remembers Gillen. “He was about seven foot tall and he looked like something out of Game of Thrones.”

Primarily shot in Belfast’s Titanic Studios, such is the scale of the show – devised by Dan Weiss and David Benioff – that segments are filmed all over the globe: Iceland, for scenes at the Wall, the 700-foot barrier that keeps Westeros (barely) safe from the zombie-like White Walkers and the tribal Wildlings; Morocco, doubling for Essos, the desert-like kingdom where Emilia Clarke’s dragon-nurturing Daenerys finds herself; and Croatia, for Westeros’s capital, King’s Landing.

So what can fans expect – apart from the unexpected? Coster-­Waldau estimates the forthcoming 10 episodes will be very Lannister-centric. “The whole dynamic in that family is very much at the core of season four,” he says, highlighting King Joffrey (Jack Gleeson), the homicidal teenage ruler, spawned from Lannister’s incestuous relationship with his sister, currently ruling Westeros’s Seven Kingdoms from the coveted Iron Throne.

With cast additions including Sherlock’s Mark Gatiss, most intriguing for fans will be the arrival of Pedro Pascal, who plays Prince Oberyn Martell, aka The Red Viper of Dorne, who – unsurprisingly – holds a grudge against the Lannisters for murdering his sister, Princess Elia of Dorne, long ago. “He’s very, very dangerous,” says Pascal, whose character looks more than handy with a sword. Factor in season four’s tagline, “All Men Must Die”, and it’s clear vengeance will be a major theme.

Take young Arya Stark (Maisie Williams), last seen stabbing to death a soldier who dared desecrate her brother’s corpse, killed during the Red Wedding massacre: “I feel like I’m playing a completely different Arya to the one I auditioned with,” says Williams, referring to Arya’s once jocular nature. “Now I feel that’s stripped away. Particularly in the forthcoming season that progresses more. She’s slowly losing that loveability about her and she’s turning into something quite different.”

This is just scratching the surface of the show’s labyrinth-like plotting. What of the Wall-guarding Jon Snow (Kit Harrington) or everyone’s favourite dwarf, Tyrion Lannister (Peter Dinklage)? The stakes, it seems, will be higher for everybody. “The intensity is building,” says Gillen. “There are, quite bravely, several parallel storylines which have yet to dovetail. And all that stuff gets closer together.”

One thing is assured: while past series have kept the shocks reserved until later episodes – beginning with the beheading of Sean Bean’s patriarch Ned Stark in season one – this time action is promised from the off. “It’s a very, very strong, action-packed first episode,” says John Bradley, who plays Samwell Tarly. “The last 15 minutes are as epic as you’ve ever seen in Game of Thrones.”

• The fourth season premiere of Game of Thrones is broadcast at 11pm tonight on OSN First HD