JK Rowling has told how she cried after killing off a "significant" character in the fifth Harry Potter book.
Rowling told Paxman she had not suffered writer's block
In an interview with Newsnight presenter Jeremy Paxman, to be screened on BBC Two on Thursday, she described how she walked into her kitchen in tears after writing the death scene for The Order of the Phoenix.
She also reveals she looks forward to a post-Harry era in her life - and denies missing a deadline or experiencing writer's block while writing the book.
The meeting with Paxman is her first and only interview before the book's release.
She says of killing off her character: "Well, I had re-written the death, re-written it and that was it. It was definitive. And the person was definitely dead.
"And I walked into the kitchen crying and Neil [her husband] said to me, 'What on earth is wrong?' and I said, 'Well, I've just killed the person'.
Rowling said she looked forward to a post-Harry life
"Neil doesn't know who the person is. And he said, 'Well, don't do it then'.
"I thought, he's a doctor you know... and I said, 'Well it just doesn't work like that. You are writing children's books, you need to be a ruthless killer'."
Bookmakers Ladbrokes on Wednesday refused to accept any more bets on the identity of the character who dies.
Ladbrokes spokesman Warren Lush said: "People out there know, it would be a licence to lose money."
Paxman also asks if he is allowed to look inside a copy of the book perched on the table.
Rowling replies: "Hmmmm. Yes a bit. You can have a look there... Yes so, that's it."
The Order of the Phoenix is awaited by millions worldwide
Asked if she finds the secrecy issue ridiculous, she says no, adding: "Well, a lot of it comes from me.
"I mean, of course one could be cynical, and I'm sure you would be disposed to be so, and say it was a marketing ploy, but I don't want the kids to know what's coming.
"Because that's part of the excitement of the story, and having sweated blood to create all my red herrings and lay all my clues... It's not my life, but it is a very important part of my life."
Speaking about life after Potter, Rowling says: "It's going to be very difficult to leave it...I do look forward to a post-Harry era in my life, because some of the things that go along with this are not that much fun.
"But at the same time, I dread leaving Harry... because I've been working on it over what I sincerely hope will prove to have been the most turbulent part of my life and that was the constant, and I worked on it so hard for so long... then it will be over and I think it's going to leave a massive gap."
Speaking about the length of time it took to write the book, she says: "Just once and for all, for the record, I didn't miss the deadline. Because there was no deadline."
"And you didn't have writer's block on that book?" asks Paxman.
"No!" she says. "I just produced a quarter of a million words!"
She also speaks about speculation over how the series might end and what would become of Harry and his friends.
"There is one thing that if anyone guessed I would be really annoyed, as it is kind of the heart of it all.
"And it kind of explodes everything - and no one's quite got there, but a couple of people have skirted it."
JK Rowling: The Interview, will be broadcast at on 1930 BST on BBC Two on Thursday.