Marion Cotillard was tough on co-star Brad Pitt while he was perfecting his French for their new movie Allied and refused to praise him for bad language.
The actress knows how difficult it is to perfect another language for a movie role and drop an accent, because Michael Mann asked her to do just that for Public Enemy, and so she decided to help Brad, who has spent many years living in France, by becoming his harshest critic.
"It's difficult when you start late in your life learning a language and you're not familiar," she tells WENN, "but it's not too late when you move to England or America and you have a total immersion. When I started learning English, I was 10 or 11, but when I did Public Enemy, Michael Mann wanted to erase my French accent, which is not really possible in this amount of time.
"I worked for six months every day basically working on one sound - the 'R', the 'L'. I spent hours in front of the mirror crying, re-educating my jaws and tongue and teeth and my whole face. It's an amount of work that is really crazy.
"Brad did an amazing job, because I know what it was to go from French sounds to English sounds, and it's the same the other way. It's super technical and super difficult. He had this commitment to do the best he could. That was really impressive. So I helped him by being tough. I was very honest with him. But at the same time I really wanted to support him."
And Pitt's language talents weren't the only things that impressed Cotillard and Allied director Robert Zemeckis, while they were making the World War Two drama.
"Brad is obviously a romantic lead actor," the filmmaker adds. "He's a leading man, he's an action actor... but the thing I was most proud of that Brad did in the movie is the way he was able to express the character's anguish and emotional pain that he was going through.
"I don't remember any roles that Brad has played where he reaches down to that place like he does in this movie."