Lily James cried the first time she met Meryl Streep.
The 29-year-old actress portrays the Hollywood legend's character Donna's younger self in the sequel, and was overcome with emotion when she was waiting to meet the 'Devil Wears Prada' star on set.
Speaking in an interview with NET-A-Porter's digital magazine, 'PorterEdit, she recalled: "[Meryl] was singing this song in a chapel and it was so emotional.
"I was sat outside knowing I was about to meet her. And crying. And it was like: 'Hold it together, Lily!' It was too much!"
The British star tried not to focus on Meryl whilst filming, but in her spare time she was cramming in research into the character and her co-star.
She said: "I tried not to focus on the Meryl Streep-ness of it all, but tried to focus on the Donna Sheridan-ness of it all.
"Having said that, I did go through all of Meryl's movies, especially stuff from when she was younger. I loved watching 'Postcards from the Edge' - there's a spunky kind of madness where she sings in that - and even 'Death Becomes Her'."
However, the screen legend made her feel at ease and allowed her have her "moment" in the movie.
She said: "[Meryl] was just so cool. We had to do this dance together and she gave it all to me, she let me take my moment."
Lily almost didn't get the part because she was planning to go to Glastonbury Festival with her boyfriend 'The Crown' star Matt Smith when the auditions took place.
Though It was "a real argument", Lily managed to fit both in.
She explained: "We went straight to Glastonbury and I think I got the part that weekend, but my agents knew not to call me, because I wouldn't have been reachable!"