Bath Literature Festival: JK Rowling on the freedom of Potter to bed, a new book for children... and her first snog

Harry Potter fans still clinging to the hope that JK Rowling may return to Hogwarts to write a prequel should take heed: it's not likely to happen.

Rowling, speaking at the Independent Bath Literature Festival last night, said she was not planning to return to the story of the "Marauders" – who attended her fictional Hogwarts School of Witchcraft before Harry Potter – because she didn't think much of prequels. "I'm never going to say never but I have no current plans. I think prequels are not generally very successful," she said.

For a bestselling novelist who is famous for guarding her privacy, Rowling was in remarkably open mood as she faced her ebullient audience of 1,600 fans. Walking out to the stage in beige trousers and a stripy top, she was greeted by uproarious cheering for the first few minutes of her appearance.

She talked about her first sexual experience (a "French kiss at a youth club disco" with a boy much older than her 12-year-old self), her writing habits ("I'm really good at writing in the front passenger seat with the three children and the dog in the back"), and the phenomenal reception of the Harry Potter series which she likened to "Beatlemania". Her own adolescence partly inspired the teenage characters in her first adult novel, The Casual Vacancy, she added, as well as her former job as a teacher.

James Runcie, the artistic director of the festival, asked her about the adult content of her latest book which encompasses gritty themes of heroin addiction, prostitution, drug dealing, online porn, self-harm and the rape of a teenage girl.

"I have never ever sat down and thought... 'now is the moment to write a book with a penis or with swearing in it'. This was a book I was burning to write… I draw on my own adolescence... and on my experience of adolescents as a teacher... I see adolescence as very fragile. When I watch my two young children, who are eight and 10, they will watch shows on Nickelodeon where teenagers are wholly false."

The Casual Vacancy is being adapted by the BBC for television.

Rowling referred to the children's book she was writing but refused to reveal much more other than that it might be for a younger age group than the Potter series: "It will be shorter. I'm very bad at estimating what sort of age group will like this... I think it might be for slightly younger children."

Rowling said she felt "utterly liberated" when she finished writing the last in the Potter series, although there was a sense of bereavement too. "From about 2000, I knew there would never be any topping Harry Potter. My publishers had got this train for the book launch which consisted of me leaving Kings Cross. I looked out at all the people screaming. It was like Beatlemania. I remember thinking 'you will never top this'. [Now], I can say 'oh, I will never top it' or I can see how lucky I am… I truly feel completely free."

Speaking of her life as a writer, she admitted to moments of self-loathing at the beginning of her career, when she would put away the Harry Potter stories for two months at a time. Now, juggling novel writing with three children and a husband, she said she craved the enforced solitude that the job requires. "One of my children said 'if it was us or the books?'. I said 'you, but I would be really grumpy'."