(AP) The mystery has been solved.
A British law firm says one of its partners inadvertently leaked the identity of J.K. Rowling as author of mystery novel "The Cuckoo's Calling."
The Sunday Times newspaper revealed over the weekend that the "Harry Potter" author had penned the book under the pseudonym Robert Galbraith, after receiving a tip-off on Twitter.
There had been speculation that Rowling or her publisher were behind the revelation. Since Rowling was outed as the author, the novel has topped best-seller lists.
But on Thursday law firm Russells said one of its partners had let the information slip to his wife's best friend the woman behind the tweet.
The firm said "we apologize unreservedly" to Rowling.
Rowling said that "to say that I am disappointed is an understatement."