Julia Roberts says it was a privilege to be able to work up close with Meryl Streep.
Roberts and Streep play mother and daughter in new dysfunctional family comedy August: Osage Country.
The movie is a big screen adaptation of the play by Tracy Letts, and sees the two Oscar winners works together for the first time.
Speaking to the Press Association, the actress said: "She is the best there is. She is really phenomenal.
"To watch her up close doing that thing, that I, like everyone, have only sat in the dark and watched in awe of. Where does it come from? How does she think of this stuff?
"To get to watch that up close and to see her be a real life person, actually working really hard to be that great, it was a privilege."
The central performances from Roberts and Streep have been winning over the critics; they have both picked up Oscar nominations for their work.
Roberts is in the Best Supporting Actress category, in what is her first Oscar nomination since her win for Erin Brockovich.
August: Osage County is out now.
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