In Game of Thrones, there is no such thing as the innocence of youth. Bran Stark lost the use of his legs after being pushed out a window, his eldest sister, Sansa, was betrothed to a brutal king, and Arya Stark has become a tortured killer before puberty and witnessed her dad's head being chopped off.
Game of Thrones might be entertainment about families, but it's not family entertainment.
Sophie Turner was 13 years old when she landed her first screen role as the naive and vulnerable Sansa Stark. ''The scenes are difficult,'' she says of the beatings and humiliation her character suffers at the hands of King Joffrey. When a storyline requires crying, Turner sometimes finds it difficult to stop.
''But at the same time, they're so much fun to do. I love working with the stunt people and it's never really a case of you get depressed or emotionally tender about it. Maybe it's just me, but I loved doing all the gritty scenes where Joffrey was, like, hitting me and the rape scene - it was all really fun. Maybe I'm just a really corrupt 17-year-old!''
Convincing portrayals help the Stark children put emotional distance between them and their colleagues.
''Jack [Gleeson] is such a good actor that he just totally changes,'' Turner says. ''You're not going to think, 'That's Jack acting' - it's Joffrey! He's a douchebag, you know?''
The big-budget series contains adult themes, strong violence, full-frontal nudity, coarse language and graphic sex scenes. So, are the young actors who appear on the program allowed to watch, or must they settle for a five-minute censored version?
''Obviously, at first I was only about 10 years old, so there were quite a few inappropriate bits,'' says Isaac Hempstead-Wright, who plays Bran Stark, the boy forced to grow up quickly after his family is torn apart. ''My parents would let me watch it but my mum sort of felt compelled to give me lectures on everything that was happening.''
Now 13, Hempstead-Wright is nonchalant about the explicit content. ''I do watch it now because I'm a bit older and I understand all the violence is just a guy behind a beheading stone pumping blood out of a fake body, so that's all sort of debunked.''
Bran spends much of season three with Hodor, the oafish halfwit entrusted to carry the young cripple away from danger. ''Every second we're not acting, we're always just having a laugh. We're always just sort of messing around,'' Hempstead-Wright says. ''So I think that also provides a good counterbalance, if you like, to the very serious, stern world that is Westeros.''
The young performers have not only won the respect of audiences worldwide but also that of their onscreen elders. Charles Dance, who plays Tywin Lannister, is a 40-year veteran of stage and screen. He shares many scenes with Maisie Williams, the 15-year old-who brings to life the irrepressible Arya.
''I was just astonished working with her because she's just so very, very good,'' Dance says. ''Her understanding of the medium and what the scenes were about, and her tirelessness, because we work quite long days - she was an absolute joy to work with.''
At the end of production of the first season, Turner and her family took home Zuni, the dog that played Sansa's dire wolf. ''I adopted the dog that played Lady, so that was actually really difficult because they just don't behave - well, mine didn't, anyway,'' she says.
Dire wolves are tenacious killers that in season one were played by a docile breed of Northern Inuits.
''The trainers are fantastic but my dog was not good,'' Turner says. ''So they just had to get rid of her. I mean, she was going to die anyway in the show but, you know, they were like, 'She's not staying on our company.' So I adopted her because she was that bad.''
Celebrity can bring lots of attention, although not necessarily at home. ''My parents are sort of fairly untouched by it, I think,'' says Hempstead-Wright, whose mother allowed him to attend six auditions.
Turner is similarly grounded by her family. ''I can't get away with anything,'' she says, adding that fame at an early age has some drawbacks. ''When I was 13 and I just got into it, of course, friendship groups at school can get a little bit bitchy. The claws are out! But you learn who your friends are and your family are always going to be there for you.''
As for what audiences can expect from Sansa as she navigates a tough new life at King's Landing, Turner is optimistic: ''It's a bit more pleasant this season,'' she says. ''You might see her smile, if you're lucky.''
Life on the edge in lands of fire and ice
Game of Thrones is supposed to be fantasy but, for the actors, the working environment is all too real. The untouched landscape of Iceland was chosen as the backdrop for the mysterious scenes set Beyond the Wall.
On set, beards snap off in the freezing cold and crew rig up in complete darkness; the limited five hours of sunlight results in a daily scramble to secure enough shots. ''It does feel like military manoeuvres,'' says John Bradley, who plays the loveable coward Samwell Tarly, whose face is regularly covered in icicles.
It takes serious money and hard work to ship equipment and personnel to such unforgiving territory, but the results are worth it. ''It is an amazingly beautiful place'', says Kit Harington, who plays Jon Snow, a member of the Night's Watch. ''There were days when we were convinced the landscape looked CGI'd.''
Season three of Game of Thrones has unprecedented scope for a TV show, using three production units in five countries, with crew members fighting each other to work in the choicest locations. Cast members were strewn across Iceland, Morocco, the US, Northern Ireland and Croatia, all in a bid to capture the vision and extreme climate of the fictional universe.
Nikolaj Coster-Waldau, who plays the morally circumspect Jaime Lannister, says of the long days shooting his storyline in Northern Ireland: ''There's a lot of rain, a lot of cold weather. But I love that stuff. You just react to whatever's thrown at you and you don't have to worry that it's too much about acting if you're almost drowning in a pool of mud.''
Richard Madden, who plays newly crowned king Robb Stark, also looks on the bright side: ''[The costumes] are covered in dirt and they stink and they don't kind of get cleaned between seasons … but they look really good and they feel good and you've worn them in.''
The cumbersome wildling outfit of Rose Leslie, who plays Ygritte, is layered with fur and boiled leather, making a trip to the toilet practically impossible. ''Forget about it,'' she says. ''Don't drink that day.''
Game of Thrones, season three, airs on Monday at 3.30pm and 8.30pm on Showcase.