AUTHOR JK Rowling changed the world with her tales of a boy wizard named Harry Potter.

Now, the wildly popular author has revealed in a new interview that she has written yet another fairytale - but this one may never be published.

Rowling, who famously wrote her first novel longhand in Edinburgh cafes, says that she scrawled the secret manuscript across her 50th birthday party dress.

She also added that the "book" now hangs in her closet.

JK Rowling reveals secret manuscript

"The theme of my 50th birthday - which I held at Halloween, even though that's not really my birthday - was come as your own private nightmare," Rowling told CNN. "And I went as a lost manuscript. And I wrote over a dress most of that book."

However, the story may never hit bookstores.

"I don't know whether it will ever be published, but it's actually hanging in a wardrobe currently," Rowling said.

The British author, whose real name is Joanne, also opened up to CNN about why she continues to use a pen name after all these years.

"I quite like JK.," she said, noting that her publisher recommended using her initials rather than her first name in an attempt to "disguise" her gender.

"I wouldn't have chosen it for that reason ... but I was so grateful to be published, if they told me to call myself Rupert, I probably would have done [it] to be honest with you."

"I actually quiet like having a pen name, because I feel that's - to an extent, that feels like an identity and then ... in [my] private life, I'm Jo Murray," she told CNN, using the surname from her marriage to husband Neil Murray. "And it feels like quite a nice separation."

News Corp Australia

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