For years she titillated Britons with her witty and erotic despatches from the front lines of the sex trade -- but the upmarket call girl, known only by the classy pseudonym of Belle de Jour, was also a canny businesswoman, parlaying her blog into a book deal and a hit TV series starring U.K. actress Billie Piper.

All the while, her true identity remained unknown. Not even her literary agent or her publishers knew.

Now the elusive and seductive Belle has been unmasked as Dr. Brooke Magnanti, 34, a research scientist in a hospital in Bristol, western England, where she specializes in developmental neurotoxicology and cancer epidemiology.

The American-born woman went public over the weekend out of fear a jealous former boyfriend was about to leak the secret. Her bombshell has provoked soul-searching and outrage among many who thought they knew her.

They include the British Army officer who was her boyfriend for seven years. Known as "The Boy" in diary entries about their sex life, he is now having to tell his family and friends the woman he hoped to marry was an escort girl who charged £300 an hour.

"I can't believe she has done this," the man, identified only as Owen, told The Daily Telegraph.

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