Agatha Mary Clarissa Christie, DBE (September 15, 1890 – January 12, 1976), was a British crime fiction writer. She also wrote romances under the name Mary Westmacott. Agatha Christie is the world's best-known mystery writer and all-time best selling author of any genre other than William Shakespeare. Her books have sold over a billion copies in the English language and another billion in over 45 foreign languages (as of 2003). As an example of her broad appeal, she is the all-time best-selling author in France, with over 40 million copies sold in French (as of 2003) versus 22 million for Émile Zola, the nearest contender. During World War I she worked at a hospital and then a pharmacy, a job that also influenced her work: many of the murders in her books are carried out with poison. Her stage play 'The Mousetrap' holds the record for the longest run ever in London, opening at the Ambassadors Theatre on November 25, 1952 and as of 2005 still running after more than 20,000 performances. Christie published over eighty novels and stageplays, mainly whodunnits and locked room mysteries, many of these featuring one of her main series characters, Hercule Poirot or Miss Marple. Although she delighted in twisting the established detective fiction form - one of her early books, 'The Murder of Roger Ackroyd' is renowned for its surprise denouement - she was scrupulous in "playing fair" with the reader by making sure information for solving the puzzle was given.