'Downton Abbey's' Joanne Froggatt talks about her blush-worthy comment to Kate Middleton

File this under royally embarrassing moments! Downton Abbey's Joanne Froggatt let her nerves get the best of her during Kate Middleton's visit to the set last year. The 35-year-old, who appears as Anna Bates in the period drama, dished to Conan O'Brien about her blush-worthy comments to the Duchess.

"You're just getting more and more nervous," Joanne said about the experience that happened when she and co-star Michelle Dockery were filming. "We're doing this scene and she's very beautiful, lovely. She has this amazing aura when she walks in the room, before we actually said 'hello' we had to act right in front of her."

She continued: "It was a little bit never racking and I got a bit jittery. So she came over to say 'hi' afterwards, and I said 'Hello, lovely to meet you' and she said 'It feels strange being in your bedroom,' because we're standing in Lady Mary's bedroom and I said 'yeah not very many people get to come in Lady Mary's bedroom' and then I thought 'Oh god, what have I just said?'"

When Joanne noticed what she said, she decided to just leave it alone, and act like it never happened. "I thought, 'Do I say? I'm just gonna be quiet, I'm just gonna be quiet." The 34-year-old royal just let the joke pass.

Joanne and the rest of the cast have wrapped taping the Duchess' favorite show, which is in its sixth and final season. Kate has made it a point to stop by and pay the set a visit before saying goodbye to the characters for good.

Downton Abbey airs on PBS Sundays at 9 p.m.