Lily James became obsessed with using a typewriter while filming 'The Darkest Hour'.

The 28-year-old actress stars as Elizabeth Layton in the critically-acclaimed movie alongside Gary Oldman as the iconic British wartime Prime Minister, Sir Winston Churchill.

Lily had lessons to use the machines and found that her fingers ''got really muscly'' and all her anxiety on set went into punching out letters.

Speaking exclusively to BANG Showbiz, James said: ''It's a real skill. I actually did six weeks of lessons.

''I had this wonderful lady come round and she was very diligent and I asked for a typewriter for Christmas.

''They [typewriters] are hard, with the keys there is a lot of pressure and my fingers got really muscly and I became really obsessive, I sort of thought if I could get the typing right it will be fine, all my anxiety went into the typing.''

'The Darkest Hour' tells the story at the beginning of World War II, as within days of becoming Prime Minister, Churchill faces one of his most turbulent and defining moments of the conflict: exploring a negotiated peace treaty with Nazi Germany, which could guarantee Britain's independence and that of the Commonwealth.

As the Nazi forces roll across Western Europe and the threat of invasion of the UK, Churchill must resist attempts by his own political party and an initially sceptical King George VI, to stand firm against the dangers facing his country and not buckle to the Nazis.

The film has received critical acclaim and Oldman recently won the Golden Globe for Best Actor in a Motion Picture, he's also been nominated for a BAFTA in the Leading Man category.

But despite the film opening to acclaim around the world, James admitted regardless of what happens with awards, she will always treasure the experience.

She said: ''It's a mad thing the awards. It does [feel great] but you know what feels even better? Just having worked with Gary Oldman, Kristin Scott Thomas, Ben Mendelsohn and Stephen Dillane, directed by JOE WRIGHT.

''Regardless of what happens now, I had that experience and I will always have had that experience and I think I have grown and learnt from it, I had such an amazing time acting and that's what I love to do so that's the real prize, as corny as that sounds.''