Following the success of Ellie Goulding's 'Your Song' on last year's John Lewis Christmas advert, the actress and singer-songwriter - real name is Amelia Warner - was selected to sing a cover of The Smiths' 'Please, Please, Please Let Me Get What I Want' for this year's festive commercial.
With said song scaling the charts and her new album Renditions - a collection '80s hits turned on their head - out this week, we met up with her to find out how she's handling her newfound fame.
Are you known as Slow Moving Millie because you're really lazy?
"I hope it's not about that! It came about because I was an actress for quite a long time and wasn't particularly happy doing it. I'd write music just for myself, and my friends were always on at me to take it further. I probably am a bit lazy too, though. I also liked the safety of writing and releasing music under a different name."
Your song 'Beasts' previously featured on the Virgin Media advert in 2009 and your latest cover is for the John Lewis Christmas advert. How did they come about?
"I did some composing for some films, which was like a transition from acting to singing. It's something I'd like to keep doing. It was a good way to start without it being all about me. After the Virgin deal I finally got some money behind me to leave acting and leap into the music properly.
"It was my manager who got me involved with the John Lewis ad. It was a situation where they knew what song they wanted and had sent it out to lots of different artists. I was recording my covers album anyway, and my manager asked me to try it out without telling me what it was for. It was about two months later when I found out it was being used for the advert."
Ellie Goulding's 'Your Song' did well last year; are you hoping for similar success with 'Please Please'?
"It's definitely a good break and it can be a great platform. There are so few opportunities in the industry now, and this is a great way to get your music out to as many people as possible. The John Lewis ad is also like the holy grail of ads, and it's a great company to be associated with."
It's quite an emotional advert - did you cry at it too?
"I've seen it a lot so I'm immune to it now, but the first time I saw it I did cry. That little boy is so cute! He's fantastic."
Your album Renditions transforms '80s pop hits by the likes of Yazoo and Tears for Fears; have you also been a fan of that genre?
"It just kind of came about. I was writing my debut album of original stuff and the covers thing was a side project. I'm randomly drawn to songs from that era because I think they often get a really bad rep. A lot are really beautiful songs but because they were written in the '80s when the production was lairy, shiny and synthetic. A lot of great ballads suffered from overeager producers. I love all of the originals, but they shouldn't have that guilty pleasure label."
We're especially a fan of your Bananarama 'Love in the First Degree' cover. Will it be a future single?
"Thanks! I love that song - I was so pleased with how it turned out. I think there's talk of releasing 'Feels Like Heaven' because it's upbeat, fun and very different from 'Please Please'.
It's a brave concept for an album; did you have any trouble convincing your label?
"I remember some of the label were concerned about me covering Bananarama because they thought no-one would take it seriously. The album isn't necessarily tongue-in-cheek, but it's about having fun. I think they work, and I don't think it should matter who did them originally or whether it's cool or not."
Does your original material have a similar sound to this record?
"There are certain tracks that are similar to my own music. The 'Don't Go' cover is quite similar to my style. My music tends to be layered up, whereas the covers here are a lot more stripped back. The two bonus tracks on the album are my own, which also serves as a bit of an introduction to my music."
Would you have ever considered applying for The X Factor?
"I don't think I could do it. I love the show and I'm full of admiration of the people who go through it, but I don't know how I could audition in front of all those people. I haven't got the backbone for it. I'd fall to pieces! There's just no way.
"I was really pleased for Little Mix, although I loved Marcus too because he's a fellow scouser. The girls just managed to out-do him on the night, whereas Marcus seemed to choke on the final. I actually quite like their version of 'Cannonball' - I almost wanted it to kick off more and become a full-on dance track! Maybe I only loved it because I was caught up in the moment - it's obviously not the ideal song for them, but who cares?"
Slow Moving Millie's new album Renditions is out now.