J.K. Rowling wrote a secret manuscript on a party dress

CHRISTIANE AMANPOUR: I read that you were considering writing a political book for children, young people?

J.K. ROWLING: Oh, that was a fairy tale ...

But I -- I will tell you this. On my 50th -- 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. And I went as a lost manuscript. And I wrote over a dress most of that book. So that book, I don't know whether it will ever be published, but it's actually hanging in a wardrobe currently.

AMANPOUR: How would you decide that this [starting her children's charity Lumos] was your mission?

ROWLING: What drew me in was one child. It was a news report about one child in a newspaper.

I was pregnant and therefore perhaps particularly vulnerable and emotional to anything to do with small children. And I'm flicking through the Sunday paper and I saw what -- still I see it in my memory. It was a very disturbing image of a very small boy screaming through chicken wire.

And I went to turn the page. I'm not proud of it, but I did go to turn the page. And then I -- I stopped and I thought, if the story is as bad as the picture looks, then you have to do something about it.

So I turned back and I read the story. And the story was about an institution in the Czech Republic where this boy, among many other children with special needs, was being kept, I would say, at least 20 hours out of 24 in a cage-bed, which is exactly as it sounds. It's a cot for a baby covered in -- covered in mesh, covered in wire. And that was his existence. And from that, that's how it all began. I was just appalled and horrified.

ROWLING: I think my worst fear, my personal worst fear, is powerlessness and small spaces. So when you think about that little boy trapped in the cage-bed, he is totally voiceless. And nobody was speaking for him.

And I think that -- we all have something that touches us on a very visceral level. I mean -- and I think that's mine. That's my thing.

AMANPOUR: And small spaces, why?

ROWLING: I don't know. I've always had that. And I think that just the idea that these children were being kept penned like this was horrific to me. But then so although I didn't think that's like Harry in his cupboard, I suppose why did I put Harry in the cupboard? Because this is my fear, being trapped and being powerless, just powerless to get out of that space. So yeah, on a very crude level, I think that news story tapped into something that I found personally horrifying.

AMANPOUR: J.K. Rowling, why the initials?

ROWLING: Oh, because my publisher, who published Harry Potter, they said to me, we think this is a book that will appeal to boys and girls. And I said, oh, great. And they said, so could we use your initials?

Because, basically they were trying to disguise my gender. And obviously, that lasted about three seconds, because -- which is wonderful. I'm certainly not complaining, but the book won an award and I got a big advance from America and I got a lot of publicity. So I was outed as a woman.

AMANPOUR: And you're a strong woman role model.

ROWLING: Well, that's right. I quite like J.K. ... I think I -- I wouldn't have chosen it. It's -- and I wouldn't have chosen it for that reason, either.

But I was so grateful to be published, if they told me to call myself Rupert, I probably would have done to be honest with you. But now, I actually quite like having a pen name, because I feel that's -- to an extent, that feels like an identity and then I'm -- in private life, I'm Jo Murray. And it feels like quite a nice separation.