Emilia Clarke and Sam Claflin were previously deemed not to have enough chemistry to work together.
The pair may star together as Louisa Clark and Will Traynor in new movie 'Me Before You' but they previously auditioned to be co-stars on another project, only for neither of them to get the parts.
Speaking on BBC Radio One, Emilia recalled: "We met six years before and it was just a series of a couple of chemistry reads together - and then neither of us getting the job! Then it worked out for us [on 'Me Before You']. We were so happy we were employed!"
The 29-year-old actress admitted she loved working with her pal but they struggled to remain serious because they are such good friends, though director Thea Sharrock didn't seem to mind because it made the love between Lou and Will seem real.
She said: "I just got to be goofy. Then amazing director Thea Sharrock - who's my favourite person on the planet - was just encouraging of it. She was like 'Yeah, do more'. And there was some stuff that I definitely just improvised.... we'd be just causing havoc. But it worked out in the end."
They shot the movie on stunning locations which made the project feel more like a "holiday" than work.
Emilia added: "Everybody is so nice in the movie and we had so much fun. We went to Majorca and went filming and I was like, 'This is a holiday'. I am not working, we are having a giggle."
The movie, which is based on Jojo Moyes' 2012 novel of the same title, follows Louisa, whose cheerful attitude is put to the test when she becomes a carer for Will, a wealthy young banker who is determined to end his life after he was left paralysed in an accident two years earlier.
His cynical outlook starts to change when Louisa shows him that life is worth living and their bond deepens, changing their lives and hearts forever.
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