Sir Peter Hall is a director, actor, and former artistic director of the National Theatre in Great Britain. He's best known for his production of stage plays, (he premiered Pinter's Betrayal and Shaffer's Amadeus) but he also has directed films (The Homecoming, Akenfield, etc.) and directed operas, like the 1983 Bayreuth Ring cycle.
In the Monday 27 March 1972 entry of his diary, he writes: "Today Edward [Hall's son by his second wife, Jacky] asked me if I believed in God. I told him I didn't but I was still trying to find out." Peter Hall's Diaries: The Story of a Dramatic Battle, by Peter Hall. Ed. John Goodwin. New York: Limelight Editions, 1985. (It was also published by Harper & Row in 1984.)
Editor's note: if anyone has a more recent quote from Hall, please send it in. I'm hesitant to add new entries to the 'atheist' category based on cites older than ten (10) years.