Lily James giggled seeing Gary Oldman as Churchill for first time

Lily James burst out laughing when she first saw Gary Oldman in costume on the set of Darkest Hour.

Gary plays British war Prime Minister Winston Churchill in the drama, and recently won the Best Actor Golden Globe, leading many to predict he’ll take home the Oscar in February (18).

Lily co-stars as Elizabeth Layton, Churchill’s personal secretary during World War II, and admits she is in awe of her older co-star for putting in such a sterling performance wearing heavy prosthetics.

"I burst out laughing," Lily told British Vogue of the first time she saw Gary in character. "I met him as Gary, we did the read through, and then on day two or three of rehearsals he came in in full prosthetics. There's a book of photos that his partner has made, and there's one that she caught of me at that exact moment with my mouth wide open.

"What he must have gone through - the body suit, the face, the neck - and to still be able to give that performance, it's extraordinary."

Lily was on hand to help Gary celebrate his win at the Golden Globes recently, and showed her support to the anti-sexual harassment movement Time’s Up by wearing a black Valentino dress.

She’ll be representing Darkest Hour for the rest of 2018’s awards season, before she begins promoting her next flick, Mamma Mia! Here We Go Again, due out in July.

"With Darkest Hour, because we were in the war rooms and underground a lot of the time, there was a sense of grind and getting through and that was quite oppressive. At the time I didn't really think about it but then making a film like Mamma Mia! where you're singing and dancing all the time, it was just a brilliant contrast,” she grinned.