You know you’re getting close to the Game of Thrones set when you’re driving through a grassy field about 45 minutes outside Belfast and suddenly the land turns white.

On closer inspection, it’s fake snow, a mixture of paper and wax, or sometimes just painted onto rocks and sprayed on grass, but it’s entirely convincing and there’s lots of it.

Then you see Winterfell.

It’s a 360-degree fortress, crawling with crew, complete with crenellations and braziers and mud and straw. What’s most notable though, is that it is a fortress preparing for war. Outside the walls, facing north, there are catapults and wooden spikes big enough to take out a dragon. Which is precisely what they are going to have to do when the war to end all wars comes as part of the eighth and final season, which debuts April 14 on HBO.

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This is the beginning of the end for Game of Thrones. At the close of the seventh season, we saw the Night King lead his army of the undead, complete with zombie dragon, south, breaching the Wall, a defence designed specifically to keep them out.

It’s not giving anything away to say that their next stop will be Winterfell. When members of the media make it to set, filming hasn’t yet begun on the grand battle between the army of the undead and the last-ditch alliance of the living — the Starks teaming up with Brienne of Tarth, the Hound, Tyrion Lannister and Daenerys Targaryen among others — but preparations are afoot.

First they have to find a way to put past grievances behind them. There have been a lot of them. We watch as Jon Snow (Kit Harington) leads his new lover, Daenerys (Emilia Clarke), into Winterfell for the first time. The looks on the faces of the Starks as they meet the woman they fear and distrust are as frosty as the landscape.

Later, we sit down with Harington and Clarke after another day in the mud and cold. They are obviously close friends — they’ve both spent most of their 20s on the show and owe their careers to it.

“It’s a strange thing thinking about life post-Thrones,” says Harington, still in the dirty black cloak and boots that is Jon Snow’s uniform. “I’ve never been in an institution as long as this, not school, not anything. The people and friends I’ve made here, the experience I’ve had, is more significant than any experience of my life thus far. It’s as big as it gets really.”

“You should have seen Kit’s face at the read-through!” laughs Clarke, in a long white fur coat. When the entire cast sat down in Belfast in October 2017 to act out the final six episodes in their entirety over two days, Harington had chosen not to read them in advance, she says. So he found out the fate of his character — and all the others — in public.

“His reactions were insane,” says Clarke. “And even for me, hearing it all come together … Everyone was crying.”

It scarcely needs saying that all of the cast are tight-lipped when it comes to spoilers. But we do know that the battle to end all battles at Winterfell is coming. The Winterfell set took 11 weeks to build and more than 50 consecutive night shoots to (we assume) destroy. And the narrative flow of the series means that, as the end comes into view, the disparate Houses of Westeros will all be brought together.

“This season we keep having scenes with people that we haven’t had scenes with before,” says Sophie Turner, who plays Sansa Stark, now ruling in the North. “I keep going, ‘Oh my God. Watching you is just so bizarre because the only time I have ever seen you in character is on TV.’ It’s really funny. I do feel like more of a fan-girl this year than ever.”

“One thing for me has been the costumes,” says Maisie Williams, who plays Arya Stark. “Seeing the costumes up close I was like, ‘God, they are so good.’ It’s every Thrones fan’s dream come true.”

Williams says that, just like the fans, she had been trying to guess the ending.

“I remember I was shooting something else earlier in the year and my mum came out to join me. We sat down one evening and we both said to each other, ‘Let’s project the final season. Let’s say who we think is going to be alive and who we think is going to be dead.’ We did and we were both wrong.”

Liam Cunningham, who plays Ser Davos Seaworth, says his agent asked him what happens in the end, then corrected herself.

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“She actually didn’t want to know what happens, because she’s a huge fan. She just said, ‘Is it OK?’ And I said, ‘Yes, we’re safe. You’re going to be happy with this.’”

Writers Dave Hill and Bryan Cogman offer similarly cryptic reassurance: “This has always been a very unique animal so I think it has an ending that fits the story,” says Cogman.

“We wanted to justify people’s investment for many years and hopefully they will not feel cheated,” adds Hill. “But we do feel a great deal of pressure to bring this thing to a satisfying close. Hopefully we’ll stick the landing.”