WATCH: Vanessa Kirby Reveals She Almost Lost Her Role in 'The Crown'

Step aside, Daniel Day-Lewis: When it comes to commitment to the craft of acting, Vanessa Kirby might just have you beat. The Crown star described how she prepared to play Princess Margaret on Late Night with Seth Meyers last night (June 14), but also let slip that some hastily applied cosmetics almost lost her the role.

"I had quite a strange screen test," she explained to host Seth Meyers. "I nearly ruined it for myself."

Noo! We can't imagine anyone else in the role, to the extent that even actual photos of the real Princess Margaret look wrong somehow. Not only did Vanessa admit she has one such photo in her bathroom, but she got so nervous at the idea of playing the royal that she ordered "every picture I could find." She promptly placed them all over her house hoping to absorb the princess's personality "by osmosis."  As if that wasn't enough, she also loves to play Margaret's favorite songs, as outlined during her 1981 appearance on Desert Island Discs.

"I'm such a desperate fan," she says. "It's embarrassing."

Despite all this preparation, it was a last-minute, hasty application of fake tan that almost lost her the role. Take it away, Vanessa:

Vanessa's departure from The Crown doesn't mean that's the last we'll see of of the actress. She's currently treading the boards in Julie in London's West End, before starring as "the White Widow" in Mission: Impossible - Fall-Out, which opens next month.

The role of Princess Margaret, meanwhile, is now in the capable hands of her age-appropriate successor, Helena Bonham Carter. She seems to have taken a rather haphazard approach to the role (although so far no fake tan related calamities have been reported), admitting to Graham Norton this week she's left just "two weeks to prepare." The revelation came in an episode of The Graham Norton Show that will air on BBC AMERICA in the U.S. on Friday 22 June.

Are you glad Vanessa got the job after all?