Madden, who played Robb Stark in HBO's
The Scottish actor, 28, stars as Prince Charming (Kit) in the latest adaptation of the fairytale, which features "Downton Abbey's" Lily James as the storybook princess and hits theaters March 13.
Coleman, also 28, doesn't appear in the film but is best known for playing Clara Oswald — The Doctor's most recent companion on the long-running British television series.
Madden has been dating the English actress since 2011 after meeting her that same year in Budapest while he was working on the BBC drama "Birdsong" and she was filming the ITV1 mini-series "Titanic," the Daily Mail reported.
The pair is rarely seen together in public but did make a joint appearance at the Berlin Film Festival last month also for the "Cinderella" premiere. (For more stealthy Richard-and-Jenna sightings, click over to this Tumblr devoted to their romance).
"The prince can't have any genitalia, apparently.... It's like a Ken doll," Madden joked of his G-rated appearance in the prince's skin-tight white trousers. "You have actresses that kind of complain that their corsets are so tight. Let me tell you something, it's nothing compared to what the boys have to go through."
"We had about two days of screen tests where we had to try lots of different jock straps, just to make sure we can't see anything through the trousers."
Kimmel's response: "Disney made you a eunuch!"