Kathryn Bigelow refused to give all her cast the full 'Detroit' script.

Hannah Murray stars as Julie Delaney in the director's new movie - based around the real life murder of three African American men during the 1960s race riots - and she revealed the filmmaker wanted everyone's performance to be ''fresh'', so kept the knowledge of who survived until the end as secret as possible

Speaking to the i newspaper, the actress said: ''Kathryn doesn't like people to over prepare.

''She likes things to feel spontaneous and fresh. Some people never got the full script, particularly the guys in the movie, she didn't want them to know if they survived or not, so the stakes felt genuinely high.''

Bigelow, who is the first female filmmaker to win an Oscar, has a number of successful movies to date and before they met Murray thought she would be an ''intimidating presence''.

She said: ''I had this idea, because of 'The Hurt Locker' and 'Zero Dark Thirty' and the intensity of those films, that Kathryn might be an intimidating presence, but she is totally the opposite.

''She is really kind and really gentle and put me at ease straight away, so it felt like an easy audition.''

The film - which also stars John Boyega, Will Poulter and Anthony Mackie - was written using court reports and eye-witness accounts of the incident in the Algiers Motel.

One of the eye-witnesses was Julie Delaney - who is played by Murray in the movie - and the actress revealed Delaney was a consultant on the set, though they didn't really speak about the events depicted in the film.

She said: ''We didn't talk about the incident much. It was more about getting to know her as a person and connecting with who she was.

''She said a couple of things that were really helpful. One was 'I was a spoilt only child and I felt that I could get away with anything ' and the other came after I asked her various questions about why she was there at the motel, 'I was just looking for a good time and I'm really not that complicated', and I found it interesting that someone sees themselves like that.''