In the 10 years since the publication of Harry Potter and the Deathly Hallows, JK Rowling hasn’t exactly rested on her laurels. The bestselling author has written four adult novels, several short stories, one play concept and a film script, as well as contributing articles to newspapers and magazines and maintaining a formidable Twitter presence.

Now, Rowling has confirmed that she’s also written most of a political “fairy tale” for young people. But according to the woman herself, we might never get to read it.

Speaking to CNN’s Christiane Amanpour, Rowling said that she penned the story ahead of her birthday party in 2015.

“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’,” she said.

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The author decided to go as “a lost manuscript”, and wrote most of the fairy tale onto a dress which she wore to the party.

“I don’t know whether it will ever be published,” Rowling said. “But it’s actually hanging in a wardrobe currently.”

Rowling went on to discuss her children’s charity Lumos – and admitted that her real worst nightmare is something much darker than a misplaced manuscript.

“I think my worst fear, my personal worst fear, is powerlessness and small spaces,” she said.

It was this phobia, in part, that motivated Rowling to create Lumos. The writer explained that she set up the charity after reading a news report about a boy in an institution in the Czech Republic, where children with special needs were kept in “cage-beds” (cots covered in wire mesh).

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“When you think about that little boy trapped in the cage-bed, he is totally voiceless,” Rowling said, drawing a parallel between the children in the institution and Harry Potter, who was famously forced to live in a cupboard under the stairs.

“We all have something that touches us on a very visceral level, and I think that’s mine… This is my fear, being trapped and being powerless, just powerless to get out of that space,” she added.

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The author, whose full name is Joanne Rowling and who privately took her husband Neil Murray’s surname, also revealed why she wrote under her initials.

“My publisher, who published Harry Potter, they said to me, ‘We think this is a book that will appeal to boys and girls,’” Rowling said. “And I said, ‘Oh, great’. And they said, ‘So could we use your initials?’”

“Basically they were trying to disguise my gender,” she continued. “And obviously, that lasted about three seconds, which is wonderful… I got a lot of publicity. So I was outed as a woman.”

However, Rowling said that while she wouldn’t have chosen to publish Harry Potter using her initials, she now quite likes having a pen name.

“To an extent, that feels like an identity and then in private life, I'm Jo Murray,” she said. “And it feels like quite a nice separation.”

Images: Rex Features / Getty