"I wanted Arthur to be really appealing without being cute, with soft hair that would make you want to pat him," is how the Arthur Christmas director Sarah Smith envisaged her lead character. Is that James McAvoy? It is now.
"I thought I was auditioning, but it turned out, I actually already had the gig, which was a bonus," is how the softly-spoken Scottish actor remembers it.
It's not surprising. McAvoy is one of the UK's most in-demand young actors, after delving into a fantasy world as the wide-eyed Mr Tumnus in The Chronicles of Narnia, opposite Angelina Jolie in Wanted, engaging with the science of X Men: First Class and brooding wartime drama in Atonement, under his belt.
Here, McAvoy voices the title role of Arthur, the younger son of the Santa Claus dynasty, in a animated Christmas fairytale. Arthur's family are charged with the duty of delivering presents to all the children in the world, with some help from 21st century technology and a million hardworking elves.
McAvoy also has animation form with the title role in Gnomeo and Juliet, although, as he describes it, the exercise of voicing a role still throws him.
"It's very strange," he reflects in London. "You're an integral part of the team and your voice creates what's happening, but you're not even there 99% of the time, and when you are, there's no one else in the room, so you feel isolated. It's a strange, disjointed process."
It definitely has its benefits though, he admits.
"It's very freeing, you can be somebody else entirely, not just in the normal way of acting, but when your physicality doesn't matter, it's just about what your voice can do. I did a lot of radio when I first started out, and it's not that different."
Plus, for McAvoy, it meant the chance to work with such British stalwarts as Oscar winner Jim Broadbent, Imelda Staunton, Ashley Jensen, Hugh Laurie and his old castmate from TV's State of Play, Bill Nighy - whom McAvoy calls "an incredibly cool, cool guy".
McAvoy already has other projects in the pipeline, from London thriller Welcome to the Punch to an adaptation of Irvine Welsh's best-seller Filth.
But if this level of success now seems inevitable for someone as diverse and appealing as McAvoy, in his own head, when did it start feeling different?
"I think The Last King of Scotland was probably the turning point," he remembers, of the epic biopic that told the story of Idi Amin and his doctor, played by McAvoy. "People saw I could be that guy who could help tell the film's story. And because Forrest won the Oscar, and it was a critical hit, it meant lots of directors and studio people saw it, and therefore saw me."
Despite his current run of success, there is no hint that McAvoy is resting on his laurels, in fact it's quite the reverse.
"The challenge is that we all want to get better, and we're all capable of being bad," he says of his increasingly high profile. "As you get more recognition from audiences and professionals alike, you're not allowed to fail, that's the hard thing. The scary thing is it can become about getting it right instead of just doing it, seeing what happens and being brave.
"Sometimes you get tempted to be less brave, do something easier. But that's not how you've got where you are, so that's the challenge. Hopefully, you've racked up enough good things, so by the time there's a bad one, they'll forgive you."Arthur Christmas is in cinemas from Friday 11 November. Watch the trailer below...