They star as lovers in upcoming gangster flick
and at one point, Sienna Miller and Ben Affleck spent nine hours filming sex scenes.
Appearing at the premiere for the Affleck-directed film, in which she plays Irish minx Emma Gould, Miller told E! about their many sex scenes, revealing they left her in tears - of laughter.
is an action-packed movie, but one which wouldn't be complete without a romantic story, for which Sienna admitted the duo were forced into a bevy of romantic scenes, the
She said: "Ben and I are like brother and sister, thank God, so there was no awkwardness. There was just a lot of stupid giggling. He's very professional-I am not, but he is.
"In that environment, it was a cool scene. There was a montage in the script saying we did it everywhere: in the car, in the bar...I was like: 'That's an entire day of just love scenes! OK. How do we do this?'
"Obviously, by the time nine hours of it has gone past, I was shaking with tears running down my face. I mean, I can't tell you-but you have to laugh. Ben is just professional. It is what it is."