Actor Eddie Redmayne has said he was concerned it would take a "different set of muscles" to play the wizard Newt Scamander in the latest Harry Potter inspired film, Fantastic Beasts And Where To Find Them.
Known for his talent at portraying real and complex characters, such as the physicist Stephen Hawking in The Theory Of Everything - for which he won an Academy Award last year - Eddie, 34, now takes on the magical world in the Harry Potter prequel, set in 1920s New York.
Speaking at the film's European premiere in London's Leicester Square on Tuesday, he told the Press Association: "I thought I was going to use a different set of muscles, but when you meet JK Rowling, the characters are so real in her mind and have such an intricate back story."
He added that he had gone to the extremes of "method" acting for his role - to the point that he was stopped at airport customs on his way back from New York earlier this week, because he was still carrying his wand.
Commenting on the situation, he joked: "Firstly, what on Earth was I doing carrying a wand? It looks like something a bit weird. They didn't seem too impressed."
He also confessed to losing the plastic film prop in his hotel room, just hours before arriving at the London premiere.
Many of the film's cast members have also admitted to being serious JK fans themselves.
Ezra Miller, who plays the misunderstood teen Credence, said that he had to fight back tears during both the European and world premieres of the film, adding that he had been thanking JK all week.
Scottish actor Kevin Guthrie plays Abernethy in the film, an employee of the American wizarding authority Macusa.
He described being involved in the film as "a dream come true".
Carmen Ejogo, who plays Macusa leader Seraphina Picquery, added: "When the first books came out I checked them out, then followed each movie as it came out. I've kept up to date.
"But I think the fun of the film is that we're all on license to go in our own directions."
Fantastic Beasts And Where To Find Them will officially launch in UK cinemas on Friday.