Eddie Redmayne may be the lead in new Harry Potter prequel Fantastic Beasts And Where To Find Them, but he's not so big as to forget his more humbling moments on screen. Susan Griffin chats to the ever-endearing Oscar winner

Eddie Redmayne might be an Academy Award winner, but he has no issue with offering up the less triumphant moments in his professional life.

Asked if he's experienced many casting flops and his quick-fire response is, "Oh God, hundreds!"

"There was Lord Of The Rings, Stars Wars...

"I remember I was meant to audition for something called 10,000 BC and then I read the script and it was about this young, ripped, tanned Neanderthal. I called my agent saying, 'Have you ever seen me?'" recalls Redmayne, 34, a man whose lean stature and pronounced cheekbones landed him a modelling contract for Burberry.

"I still auditioned for it, but didn't get the part!"

As a student, he also unsuccessfully auditioned for the role of Harry Potter's Tom Riddle. "I don't think I even got to meet the casting director, I got the casting director's assistant's assistant," he says, laughing.

Fast-forward to today and he's the lead in Fantastic Beasts And Where To Find Them, a prequel of sorts to Potter's wizarding world.

The movie is directed by David Yates, who helmed the final four Harry Potter blockbusters, and is J.K. Rowling's first screenplay.

The story's inspired by the 2001 book she wrote under the guise of fictitious author Newt Scamander, a Magizoologist who describes the wondrous creatures that populate the magical universe.

Newt's even referenced in the first novel of Rowling's series when Harry Potter reads his book at Hogwarts.

While Rowling reportedly wrote the script in 18 days, Redmayne took a few months to prepare for the role.

"Hilariously, in the script J.K. Rowling had written, 'Newt takes off his shirt'. When I read that, it was like, 'Oh b*****ks!' It was six months at the gym eating nothing but chicken - all of that, and then the scene was cut from the film. That was a bit depressing," says the actor, who reveals he also needed time to feel comfortable in a world strewn with special effects.

"I'm crap with green screen. I have a bad imagination," insists Redmayne, who won an Oscar in 2015 for his role as Professor Stephen Hawking in The Theory Of Everything, and was nominated again earlier this year for his performance as a transgender pioneer in The Danish Girl.

"Some actors could turn up on the day and talk to tennis balls and it would all be fine, but I don't have a good enough imagination. The great thing about our job, however, is you can use playing a character as an excuse to have fun, so I went to wildlife parks and met people who handle animals."

In Fantastic Beasts And Where To Find Them, the action's set in Twenties' New York, and follows British-born Newt's adventures as part of the Big Apple's secret community of witches and wizards.

Redmayne admits nothing could prepare him for walking onto the epic set at Leavesden Studios [home of the Harry Potter movies] to witness first-hand the sheer scale of the movie, the first of five.

His open-mouthed amazement rendered the first take "completely useless".

"There were big cranes, maybe 500 extras, cars, smoke coming up from potholes. The scale of it was like a different age of movie-making. I'm used to smaller-scale films and it was completely awe-inspiring."

A fan of the Harry Potter films, he describes it as "weird to deal with the machinations" of what goes into bringing these fantastical films to life.

"We've seen that phenomenal duel between Ralph Fiennes [Voldemort] and Daniel Radcliffe [Harry Potter], but when you have to engage in something like that yourself, you're standing there with a wand and a wind machine and you realise how extraordinary those guys were," says Redmayne.

His decision to star in the movie had nothing to do with becoming a father.

"Having a child does genuinely seem like magic. That probably sounds quite saccharine," grins the actor who welcomed a daughter with Hannah, his wife of two years, in June.

"But when I was cast in this, I don't think Iris was a figment in anyone's imagination. For me, it's all down to the script and when I read this script, I was blown away by it. It was unlike anything I'd read and I was completely intoxicated."

A man who enjoys the "cinematic experience in all of its guises", he adds: "What's wonderful about this is the writing is excellent and you care about the character.

"It's not enough nowadays for it just to be bells and whistles. For all the action, the fantasy, the darkness, the comedy, at its heart, it's an incredibly emotional story and that's what pulls you in."

Born in London, Redmayne combined his schooling at Eton, where he was in the same year as Prince William, with stage roles.

"I loved it, principally because it meant I could leave during the middle of maths class, and go to the West End and do a play," he recalls.

On graduating from Cambridge University, he appeared in TV's Doctors, Elizabeth I and Tess Of The D'Urbervilles, and earned small parts in movies such as Elizabeth: The Golden Age and The Other Boleyn Girl.

The male lead in 2011's My Week With Marilyn and World War One drama Birdsong followed, as did an opportunity to showcase his singing talents in 2012's Les Miserables, before the script for The Theory Of Everything landed in his lap.

Despite the plaudits, Redmayne prefers to downplay any notion of celebrity, though he admits: "Sporadically there are moments of insanity."

...Like travelling on the tube and realising someone's taken a photo under the pretence of texting, for instance.

"You stare at them and they stare at you because you're both slightly shell-shocked and you have 40 seconds before you arrive at the next station," reveals Redmayne.

"That's the level of oddness of it, coupled with suddenly then turning up at Comic Con where thousands of people are specifically there for that. It's quite discombobulating, but 99 per cent of the time, it's super-normal," the actor explains.

And, as he points out, there's nothing you can do to prepare for fame.

"What are you meant to do?" he says with a laugh. "You just stumble through, I think."

Fantastic Beasts And Where To Find Them is released on Friday, November 18