Image copyright 20th Century Fox Image caption [L-R] Roman Griffin Davis, Taika Waititi and Scarlett Johansson star in the film which satirises Hitler

Child actors can be a bit of an unknown quantity as interviewees, but Golden Globe-nominated Roman Griffin Davis is pretty relaxed about his new-found fame.

Self-deprecating and confident, the 12-year-old stars in satirical film Jojo Rabbit as a Hitler Youth fanatic.

The movie explores the fall of Hitler through the eyes of Roman's 10-year-old character Jojo, whose glamorous mother is played by Scarlett Johansson, while Thor: Ragnarok director Taika Waititi appears as a ridiculous Hitler.

New Zealander Waititi also wrote and directed the film, along with the critically acclaimed Hunt for the Wilderpeople, and Marvel fans may recall his comic turn as motion character Korg in Avengers: Endgame.

Jojo Rabbit has had some mixed reviews, but it's nominated for a Golden Globe and it did win this year's People's Choice award at Toronto Film Festival, which can bode well for future success. Several previous Toronto audience winners have gone on to win best film at the Oscars, including Green Book (2018), 12 Years a Slave (2013) and Slumdog Millionaire (2008).

British actor Roman is extremely excited about the Golden Globes ceremony on 6 January, where he plans on "dressing like a waiter" so he can visit all the tables where his screen idols will be sitting, and meet them personally.

But despite his jokes, he's very serious about the film itself, and why youngsters today need to know how Hitler "brainwashed" young German boys such as Jojo.

The Hitler Youth was created in 1922 to indoctrinate youngsters into Nazi ideology and train them as tools of war.

Image copyright 20th Century Fox Image caption JoJo has to practice shouting "Heil Hitler" a lot [L-R: Roman Griffin Davis and Taika Waititi]

"I won't name names but in some politics, they're spreading hate through the internet, that's spreading hate unconsciously. And I think it's just for the next generation they need to know that their hate can really do damage," Roman says.

"Taika told me about Hitler brainwashing children, we saw it as like a layer of paint going over the child.

"Jojo was brainwashed but he was an innocent kid, he wasn't always bad, so I tried to show that."

Roman makes a startling comparison between young Jojo and the Hulk, saying flashes of the real person underneath can spark through, just like David Banner occasionally breaks through from being the Hulk amidst all the anger and chaos.

"I'd try to keep moments where you could see the real child, like the Hulk with this mutant layer on him, and every now and then he quirks out of it."

Image copyright 20th Century Fox Image caption [L-R] Stephen Merchant, Alfie Allen, Sam Rockwell and Roman all play Nazis

Reflecting on the Hitler Youth, Roman says: "What the Nazis did to children was really awful.

"They wanted to have an army of fanatics to help them take over the world. I know now there were 16-year-old soldiers on the front lines - and they were terrified but often the bravest, and so many were killed."

Jojo is aged just 10 in the film, and his life as a budding Nazi becomes complicated when he finds an opinionated, smart Jewish girl called Elsa (Thomasin McKenzie) hiding in his attic. Their relationship is unusual, with the balance of power constantly shifting between them.

Image copyright 20th Century Fox Image caption Thomasin McKenzie plays a Jewish girl living in Jojo's attic

The film is also punctuated by bizarre scenes with Jojo's imaginary friend Hitler (Waititi) along with quirky yet menacing Nazi officers played by Rebel Wilson, Sam Rockwell and Stephen Merchant.

Casting Jojo wasn't easy - Waititi and his team saw more than 1,000 audition tapes from New Zealand, Australia, the UK, the US, Canada and Germany. But when they met Roman they knew he was the one.

The young star's previous acting experience was limited, though. "I played a tree in the school play and did one song in the background," he explains.

But despite this, producer Carthew Neal says Roman's audition was "just incredible", to which the young star deadpans: "I fluked it."

Image copyright 20th Century Fox Image caption Roman and Taika Waititi filmed together on set in the Czech Republic

Roman was helped during filming by acting coach Rachel House, from the cast of 2002's Whale Rider, and both his parents are in the film business, so he felt at home on set.

His mother is writer-director Camille Griffin and his father is cinematographer Ben Davis, whose recent films include Guardians of the Galaxy, Avengers: Age of Ultron, Doctor Strange and Captain Marvel.

"My Dad has always been on film sets," he says, adding he loved meeting Benedict Cumberbatch and Chiwetel Ejiofor on the set of Doctor Strange, adding the food on Marvel sets is "amazing".

Neal says the film-making process could have been precarious, given they had to "rely on this 10-year-old to pull it off" but after seeing Roman's angry scenes, he thought "yes, we're going to be OK".

Image copyright 20th Century Fox Image caption Roman was surrounded by seasoned actors, including Sam Rockwell and Scarlett Johansson

The whole crew avoided putting pressure on Roman and "kept it all very relaxed," and the young actor explains: "Honestly, I just had to say the lines of the script, it had so much in it and it really spoke for itself."

Working closely with Marvel and Marriage Story star Johansson also helped Roman's performance.

"She was a child actress and she's now a mother - she could tell I was a bit nervous and scared about playing this character so she really helped me. She was always supportive and she's a clever person," he says.

Playing a Nazi didn't come naturally to him though, because it "felt so wrong to find such strong feelings and go on pro-Nazi rants".

The film, inspired by the 2008 book Caging Skies by Christine Leunens, has polarised some critics and famous names.

The Guardian's Peter Bradshaw gave it one star, saying: "There's nothing wrong with refusing to take Hitler seriously, of course, but this film doesn't have the passion of Charlie Chaplin's The Great Dictator or the satirically magnificent bad taste of Mel Brooks's The Producers. There are no insights to be had - and no laughs."

Mel Brooks didn't appear to agree though, saying: "I think I'm going to send Waititi a note to tell him, 'Good job. Well done'."

The New Yorker called it "the world's unfunniest comedy" but Variety called it a "feel-good hipster Nazi comedy, adding: "It's this year's model of Nazi Oscar-bait showmanship: Life Is Beautiful made with attitude."

Director and actor Jon Favreau, whose work includes various Marvel films and The Lion King, was clearly a fan.

"I love when filmmakers are not afraid to throw themselves into a triple axel, not knowing if they can land it. It is one thing to challenge the formula in a Marvel Thor sequel. It is quite another when you're painting a sympathetic portrait of kids coming of age while being corrupted by the Third Reich," he said.

Image copyright 20th Century Fox Image caption Rebel Wilson (right) played her role for laughs

Roman thinks the film has an important message.

"I showed this film to my all classmates at our local cinema," he says.

"Once the film finished, I asked these kids, who didn't know what the Holocaust was, what they thought the moral of the film was, and this one kid said, 'See things through your own eyes and not someone else's'."

He adds: "What I love most about the film is that even though it is about some heavy stuff, and stuff that's really important, a lot of it is shown through humour and comedy."

JoJo Rabbit is now out in the UK and Ireland.