Lily James found working with Gary Oldman ''depressing'' because he's so talented.

The 29-year-old actress stars alongside the Oscar-winning star in the Joe Wright-directed war drama 'Darkest Hour', and Lily admitted that after seeing such an accomplished performer in action, she reconsidered how she approached her work.

Asked about the experience of working with Gary and subsequently, Meryl Streep on 'Mamma Mia! Here We Go Again', Lily shared: ''Well, you sort of learn that what they do is not learnable - and that is depressing.

''It's a skill to be so fully invested in the moment as it's happening. I saw what they do in between to garner and muster up that energy and I tried to figure it out.''

Lily's latest role sees her star as author and protagonist Juliet Ashton in the historical drama 'The Guernsey Literary and Potato Peel Pie Society'.

But the British beauty - who previously appeared in hits such as 'Baby Driver' and 'Cinderella' - initially rejected the role.

She told The i newspaper: ''I was just about to start a Second World War film, 'The Exception', and I felt like I wanted to move out of doing period dramas, or at least try to explore different avenues.''

But Lily ultimately performed a U-turn because she realised that Juliet - who helps to investigate the fall-out from the Occupation of Guernsey by the Nazis - was actually a ''modern woman''.

She shared: ''It also felt like a step forward in that she is a more mature woman. She's a writer, she's ambitious and she has everything going for her. She feels like such a modern woman.''

Meanwhile, Lily revealed earlier this month that she cried the first time she met Meryl.

The actress - who portrays the Hollywood legend's character Donna's younger self in 'Mamma Mia! Here We Go Again' - said: ''[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!''