ON JULY 14th a British newspaper revealed that "The Cuckoo Calling", a crime novel ostensibly by an ex-serviceman called Robert Galbraith, had actually been written by J.K. Rowling, the author of the "Harry Potter" series and the first female novelist to become a billionaire. The fallout has resembled a whodunnit itself. Who first revealed the secret to whom has become as interesting, to the media at least, as the quality of the book (which immediately shot to the top of the bestseller lists). Why do some writers use pseudonyms?

Many people write under an assumed name. Indeed all the columnists for The Economist—Bagehot, Lexington, Schumpeter and the like—write under inherited pseudonyms. For novelists this practice has long been widespread. In the 19th century Mary Ann Evans took on the name George Eliot in order to separate her novels, such as "Adam Bede" and "Middlemarch", from flowery female-novelist stereotypes. In America around the same time Samuel Langhorne Clemens published fiction under the name Mark Twain (pictured above, with Eliot and Ms Rowling). Novelists who want to write crime fiction on the side have long masked their identities. John Banville, an Irish novelist who won the Man Booker prize in 2005, writes crime novels as Benjamin Black. Julian Barnes, another Man Booker-winning author, writes thrillers as Dan Kavanagh. And crime writers themselves may also take on different personas. When Agatha Christie, one of the masters of the dagger-and-cyanide genre, wanted to write romantic fiction, she did so as Mary Westmacott. Patricia Highsmith, the author of "The Talented Mr Ripley", a gruesome thriller of swapped identities, published "The Price of Salt", a lesbian romance, under the name Claire Morgan.

Three main reasons spurred these writers to take the name of someone else. A pseudonym gives them the liberty to write things they might not otherwise feel able to. It gives them an opportunity to be taken seriously, something especially important to female authors in a world of Victorian male critics, or to dabble in a genre that, despite the work of great crime writers like Raymond Chandler, is still not really considered to be proper literature. Most of all, a pen-name distances established authors from their previous work.

J.K. Rowling says on her website that her decision to publish as Robert Galbraith came about because she wanted to "go back to the beginning of a writing career in this new genre, to work without hype or expectation". To be taken seriously was only part of the point (indeed, Ms Rowling has already published a serious novel for adults). More important was the sense of being unknown, perhaps valuable for someone who masked her own name in gender-neutral initials when she started out as an author. But for one of the world's best-known writers, the delightful sense of being anonymous will probably continue to remain elusive.