Like many other Oxford students, Anna Popplewell was last week marking the end of her university exams – typically with a round of parties or punting. Next week, the teenager will enjoy a rather more high-profile celebration when she dons a glitzy dress to tread the red carpet at what is being billed as one of the biggest-ever film premieres to be held in Britain.

Up to 10,000 people are expected at Thursday’s London screening of Prince Caspian, the second of CS Lewis’s seven Narnia chronicles to be adapted by Disney for the cinema.

For young fans, it will be a magical glimpse into the kingdom of Narnia – the fantastical world of talking creatures into which the four Pevensie siblings are once again transported for another heroic adventure. For the young stars who play the Pevensies – William Moseley, 21, Popplewell, 19, Skandar Keynes, 16, and Georgie Henley, 12 – it will be a chance to revisit, as Popplewell puts it, “the memories of filming it, the locations, the in-jokes, the lines we may have cocked up in shooting”.

Thursday’s screening also marks an end to five years’ hard work for these four young actors – a journey that began in 2003 with auditions for The Lion, the Witch and the Wardrobe, the first Narnia film. For the sequel, they spent long days on set in New Zealand and eastern Europe, did stunts with swords and horses that left them with scraped knees, and then endured tiring publicity tours.

While landing a part on such a big production may be every young actor’s dream, the reality for the families involved has been rather more mixed. How do you keep up with homework while filming “in the middle of nowhere”? How do you cope with the pressures of fame – or, for that matter, failure, if a multi-million-pound film flops? And how does it affect a mother when she has to chaperone her child abroad for weeks at a time?

Sitting in an Oxford cafe a stone’s throw from Magdalen College where she is a first-year undergraduate, Popplewell laughs when I ask about her parents’ original reaction to the news that, at the age of 14, she had won the part of Susan, the bossy, practical, older Pevensie sister.

My parents, says Popplewell, are not pushy stage-struck types, not “the kind that turn up at auditions and sit in the waiting room with curling tongs plugged in”. Her mother, Debra, is a doctor at Great Ormond Street hospital; her father Andrew is a QC. And her grandfather, the retired High Court judge Sir Oliver Popplewell, is best known for his inquiry about what the athlete Linford Chris-tie kept in his lunchbox.

When Anna fell in love with acting at the age of six after attending a local drama course, she asked to attend professional castings. However, her family was sceptical. “They felt that it was a difficult thing for a young child to handle rejection,” recalls Popplewell, who is tiny and has large, pouty lips. She eventually won them round, but they insisted that she continue going to school.

So when she was chosen as Susan, it became clear that a big hitch (apart from having to field media questions about her first on-screen kiss with Caspian, played by 26-year-old Ben Barnes) was the prospect of two long breaks from her studies. The filming of The Lion, the Witch and the Wardrobe fell during her GCSEs; the filming of Prince Caspian in her A-level year.

“Any parent would be concerned about a child missing one term of school in a public exam year,” says Anna, who was under added pressure because her place at Oxford depended on good A-level results. A solution was found when teachers from her London girls’ school agreed to fly out to New Zealand in the holidays to coach her; she subsequently scooped three A grades.

Although the film company provided daily tutoring (albeit occasionally in tents and camper vans), education was a general concern for the young stars. Each one had been a pupil at a mainstream school; each had started drama classes only as an extracurricular activity.

William Moseley, who is now building an adult acting career, was so keen to land the part of Peter Pevensie that he actually left school to rehearse at home with his mother for the auditions. However, the parents of the others were keen that their children should continue to combine school life with acting – a decision that has kept the young stars remarkably level-headed while leaving their career options open.

Both Georgie’s and Skandar’s parents initially balked at allowing their youngest children to accept the parts of, respectively, Lucy and Edmund Pevensie. Georgie’s mother Helen says that she and her husband Mike, an IT lawyer, “considered withdrawing Georgie, then eight, from the process” because of the potential disruption to family life. “The director had to have dinner with my mum and dad to persuade them,” recalls Georgie.

Skandar’s parents actually forbade their son from auditioning. “My parents told my agent not to send me: they had heard it was six months in New Zealand. But then they went to Japan for 10 days, and my grandad was taking care of me . . .” reveals Skandar. His mother Zelfa Hourani takes up the story: “The fact that we would have to be away for six months on the other side of the world would have meant dividing our family – my first reaction was that it was out of the question.” But Zelfa was persuaded by her daughter to back down: “She said Skandar would never forgive us for passing up the chance of being in the film.”

And so, after early misgivings the families threw themselves into helping their children enjoy what Skandar describes as “a chance in a million”.

While Anna’s parents split the months on location abroad with friends and godparents – who stood in as chaperones – Georgie’s and Skandar’s mothers largely stayed with their children.

Without the support of her mother, admits Georgie, she doesn’t think she would have coped very well. In New Zealand, Helen turned their house into a home – “I loved my room: it was yellow with giraffes on the wall-paper,” says Georgie.

The parents also ensured that birthdays were celebrated. Anna’s 16th, on the set of the first film, was organised by Zelfa. “We were on South Island in New Zealand, staying in log cabins, and Zelfa filled her place with lupin flowers, and got a sushi chef. We even had a chocolate cake,” says Anna.

It helped that everyone on set behaved as if they were part of a big family. The children, who have effectively grown up together, have stayed good friends and keep in touch by e-mail. Georgie and Will live outside London – but even now, when they come to the capital, Zelfa will make a big meal for them . “It sounds cheesy, but [we] are like a real family,” says Georgie.

None of the children seems spoilt. Skandar, who wants to be a doctor, agrees to meet up with me on the day of his GCSE English exam. In Oxford, Anna, who is reading for other acting roles in the holidays, is completely unfazed when the strap of one of her LK Bennett sandals breaks and she has to teeter up the high street. And Will, despite obvious jet-lag, is charm itself when he lands after a five-hour flight.

“You have to be careful when you get involved in something like this not to let your head get too big,” says Georgie. “You can’t go back to a normal life if your head is too big.”

All of them, of course, have reaped financial benefits. Although Anna says that the money is “not as much as people would think”, Skandar acknowledges that his parents won’t now have to worry about paying to put him through college.

As Skandar and Lucy prepare to shoot the third Narnia film in the autumn, Anna and Will are bowing out because their characters appear only in the first two books. “ I am very sad. It’s been a big chunk of my life,” says Anna. Will says: “For us four children, it was totally the right choice to make these films.”

Do the parents agree? Despite initial reservations, the answer is yes. “It has been an amazing experience,” says Helen Henley.

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