Clement Attlee was a British Labour politician who served as the Prime Minister of the United Kingdom from 1945 to 1951, and as the Leader of the Labour Party from 1935 to 1955. In 2004, he was voted the greatest British Prime Minister of the 20th century in a MORI poll of 139 professors. 
"[...] then in 1896 at the age of thirteen went on, like all the boys in the family, to Haileybury College. Here he confirmed an unobtrusive atheism—he became disenchanted with church attendance and religious observance—and played rugby and cricket with the handicap of his small stature and lack of any real skill, but enjoyed the rifle corps."
- Passage from R. C. Whiting's article, 'Attlee, Clement Richard, first Earl Attlee (1883–1967)', Oxford Dictionary of National Biography, Oxford University Press, Sept 2004; online edition, January 2008 (accessed 2 May 2008). 
From the book Clement Attlee by Jerry Hardman Brookshire (pp. 15):
Attlee: I'm one of those people who are incapable of religious feeling.
Harris: Do you mean you have no feeling about Christianity, or that you have no feeling about God, Christ, and life after death?
Attlee: Believe [sic] in the ethics of Christianity. Can't believe in the mumbo-jumbo.
Harris: Would you say you are an agnostic?
Attlee: I don't know.
Harris: Is there an after-life, do you think?