The handsome actor – who played Robb Stark in Thrones - is the Prince Charming in Disney's brand new liveaction telling of the Cinderella fairytale.
But speaking on ITV's This Morning today, he admitted he initially had no idea what the role was…
"I got the email through and I thought 'oh God, am I going to do pantomime?'... there's nothing wrong with that, but I just thought 'is that what I'm doing next?" he recalled.
"My agent had just had a baby and I thought he'd gone soft, but then I read it and thought it's great. And then [I was told] that Kenneth Branagh was directing and Cate Blanchett and Helena Bonham Carter were in it and I was like, 'right, sold!'..."
Sir Kenneth Branagh's retelling of the classic fairytale stars Downton Abbey's Lily James as Cinderella.
Lily and Richard both walked the red carpet in Leicester Square for the London premiere on Thursday night (19 March).
"We are used to being on stage and on camera - but when you're being yourself on the red carpet in Leicester Square you get kind of terrified," he said.
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