Which moment embarrassed you most?

Appearing on a Paris catwalk in a beard.

My brother was singing Yellow Submarine on stage with his class. I was singing along with them, showing off cos I knew all the words. The song ended suddenly and I was the only one in the whole hall who sang, 'We ...'

One time I got so drunk in the Soho theatre in London that I fell asleep in the disabled toilet for two hours. People still call the toilet Rosie’s Bedroom.

Missing a cue on stage. I had to come on and move a piece of furniture with another actor and I completely forgot. I looked at the monitor and said, “Why is he standing on his own?” And somebody said, “Aren’t you meant to help him?”

I was bumped as a guest on The Justin Lee Collins show for Bianca from EastEnders.

I once did a record store signing in LA, which I had no business doing. No one was there – just staff. They were getting ready to close the shop and sweeping up.

Forty-eight hours after giving birth, I sent a picture that someone had sent me of their baby to a WhatsApp group, thinking it was my son (they kind of looked similar). Mortifying.

In order to raise money to pay for myself to go to the National Youth Theatre, I performed a medley of my drama school speeches and some songs for my entire school. Considering I can’t sing, this was terrible. I did U Remind Me by Usher and Hey There Delilah by the Plain White T’s. They paid £2 each – basically, to laugh at me.

At the TV Baftas last year I was wearing these heels that had stiff bows on the front. One heel locked into the other bow and I went arse over tit.

I once asked a young woman if she had ever heard of the musician Laura Marling, insinuating I knew Laura Marling, to which she replied: “I am Laura Marling.”

I’ve never seen Star Wars (I know!) and on my first day of a recent job, I’m sitting next to this very friendly actor. I ask if he has much experience with motion capture. He says, “Yes.” I say “Oh great! What have you worked on?” He says, “I’m Mark Hamill.”

When I was 11, I went down a water slide and my bottoms didn’t go with me. Everyone saw my bare white butt.

Rapping the Humpty Dumpty nursery rhyme on national television.

Falling flat on my face in Billy Elliot on Boxing Day when I was 14. I fell smack bang at the end of my number. I was mortified.

At the Mighty Hoopla festival, Kimberley and Nicola from Girls Aloud joined me on stage for a Girls Aloud song. I completely forgot the words.

Helen Mirren was in the elevator with me at the National Theatre. She pressed the button but it didn’t move. I said, “Fancy seeing you here and being stuck in an elevator.” And she said, “Was that meant to be funny?” I apologised, and she laughed. Even talking about it now, it feels so awkward and embarrassing.

One of the first TV appearances that our band made in America, on the Craig Ferguson show. I forgot the lyrics to Little Lion Man and then broke two strings.

When my trousers split on stage in Burn the Floor in Australia. I had always been warned to wear my flesh underwear and I did not that day.

In my 20s I was in a show called The Unauthorised Autobiography of Samantha Brown. The actor who played my dad messed up his lines and it made me laugh so hard that I ended up peeing my pants.

Congratulating Dua Lipa on managing to release a single in such a tough industry, because I thought she was a struggling indie artist. I Googled her the next day and realised that she has 88 million followers.