In leafy Dulwich, south London, four stars from Game of Thrones convene in a Georgian house for Vogue.With the sky outside a anamur eskort washed-out grey, the jewel-like colours of their Balenciaga and Givenchy gowns are almost obscenely bright. In the fictional world of Westeros, a mighty gathering such as this would be a prelude to war. After all, these women play four of the strongest characters on the blockbuster HBO series that helped revitalise the TV landscape, launched a thousand water-cooler conversations, won 47 Emmys and turned a generation of British talent, including this foursome, into bankable global stars.

If Game of Thrones proves anything, it’s that it requires full commitment – to gore, intricate plotting and gargantuan world-building – to craft a cultural phenomenon. Same-day viewers quadrupled since the first season, in 2011; cross-platform numbers for the seventh season averaged 30.6 million viewers per episode – more than the populations of Greece and Belgium combined; and for seven consecutive years it was the world’s most pirated TV show. Fans breathlessly pore over every last detail that emerges from the notoriously tight-lipped set, right down to the size of the green screens being used or the choice of crown deployed for each character. The series has dispelled the idea that fantasy is solely for male dweebs. It’s no understatement to say that the forthcoming eighth season – the show’s final six installments – is the most exciting TV comeback of the year.Maisie Williams, 21, who turned up earlier in leopard-print Dr Martens, is already on the lookout for Turner. Both young actresses have fan armies of devoted teens who have jointly crowned them #Mophie, but it appears no one is more devoted to the pair than the girls are to each other. “Is she here yet?” asks Williams, letting out an elated cry when she is informed that her best friend from the show is, indeed, present.

Williams and Turner were only 12 and 13 when they were cast respectively as sisters Arya and Sansa Stark, the former a tomboy turned assassin, the latter the brat who matured into the queenly Lady Stark of Winterfell. Their lives have changed in real life, too, of course. Filming aside, Turner is engaged to the musician Joe Jonas, while Williams has launched Daisie, a social networking platform for creatives.

As the new season begins, Williams, Turner and Christie’s characters are hunkered down in Winterfell, the ancestral castle of the Stark clan. The army of the dead – led by terrifying supernatural warriors known as the White Walkers – are marching towards them. Further south, Cersei – newly pregnant by way of her long-term sexual relationship with her twin brother, Jaime – is plotting to wipe out the Starks and any other threat to her reign.

Understandably, there is a whiff of battle-hardened weariness to the group. The final season took 10 months to film, including a much-hyped fight scene that was shot outdoors for 55 nights before moving to a studio for further weeks. “All the training in the world couldn’t have prepared me for the amount of stamina you needed for these night shoots,” Williams says. “It gets to the point where it’s four o’clock in the morning and you’re looking around like, ‘This is ridiculous. What are we doing?’”

When Game of Thrones premiered, much was made of its no-holds-barred approach to female nudity, rape and violence. Turner’s character, Sansa, in particular, was put through the wringer – she was first betrothed to abusive boy king Joffrey Baratheon, then married off to psychopathic sadist Ramsay Bolton. Her rape at the hands of the latter, in particular, had viewers up in arms. “There are some people who make comments like, ‘It’s a misogynistic show because all these women are getting raped,’” she says passionately. “[But] most of the people coming out on top are women.” Williams agrees: “I’d say the key players this season are all female, which is why it’s so amazing we’re doing this shoot today.”

As for the wrap party? In keeping with the House of Stark’s famous motto, “Winter Is Coming”, HBO booked Snow Patrol to play for the cast and crew in Belfast; footage later uploaded to Twitter shows a tipsy crowd singing along to the show’s distinctive cello theme. “Goodbye, Belfast,” Williams posted on Instagram on the last day of shooting. “Goodbye, Arya. Goodbye, Game of Thrones. What a joy I’ve had.”