None other than Harry Potter author, J.K. Rowling, has been revealed as Robert Galbraith, author of murder mystery 'The Cuckoo's Calling'.

The amazing news was reported over the weekend by the Sunday Times, which was tipped off by a tweet from account@JudeCallegari, which quickly was deleted, and the book swiftly reached up to the top of the best-seller charts.

J. K. Rowling is a British novelist, best known as the author of the Harry Potter fantasy series. The Potter books have gained global fame, won multiple awards, and sold more than 400 million copies. They have become the best-selling book series in history, and been the basis for a series of films which has become the highest-grossing film series in history.

That tipster whose tip led to this unravelling, first was revealed by The Standard to be Judith Callegari, a mother of two from Surrey, England. Callegari's husband, Paul Callegari, is a partner at the law firm K&L Gates.

But how did Callegari learn of the truth behind Robert Galbraith, billed on the dust jacket as a former member of the Royal Military Police "who was later attached to the SIB (Special Investigative Branch)?"

The answer: Her best friend is a woman married to Chris Gossage, a partner at another firm, Russells Solicitors, that reps Rowling.

The revelation has resulted in a statement of apology from the firm to its billionaire author client.

"We, Russells Solicitors, apologise unreservedly for the disclosure caused by one of our partners, Chris Gossage, in revealing to his wife's best friend, Judith Callegari, during a private conversation that the true identity of Robert Galbraith was in fact JK Rowling," it reads.

"Whilst accepting his own culpability, the disclosure was made in confidence to someone he trusted implicitly. On becoming aware of the circumstances, we immediately notified JK Rowling's agent. We can confirm that this leak was not part of any marketing plan and that neither JK Rowling, her agent nor publishers were in any way involved," the statement continues.

Rowling has issued a statement of her own, expressing her profound regret over the exposing of the well-kept secret.

"I have today discovered how the leak about Robert's true identity occurred," she said Thursday. "A tiny number of people knew my pseudonym, and it has not been pleasant to wonder for days how a woman whom I had never heard of prior to Sunday night could have found out something that many of my oldest friends did not know."

"To say that I am disappointed is an understatement. I had assumed that I could expect total confidentiality from Russells, a reputable professional firm, and I feel very angry that my trust turned out to be misplaced."

The book, about a war vet-turned-private eye, is published by Sphere, an imprint of Little, Brown.