Harry Potter author JK Rowling, photographed in 2005.Christopher Furlong/Getty Images

Record-breaking author J.K. Rowling has remembered the moment she first realised that, in her schoolboy wizard Harry Potter, she had created a phenomenon.

Rowling’s series of seven books telling the trials and triumphs of Harry and his friends at Hogwarts School for Wizards has now sold more than 500 million copies across the world and been turned into a film franchise worth more than $10billion, but back in 1997, when her first book Harry Potter and the Philosopher’s Stone (called ‘Sorcerer’s Stone’ in the US) was published, it all felt very different.

Rowling told The Sunday Times newspaper that it all felt like a bit of a blur, until she won the Smarties Book Prize in 1997. “Then I got a record advance from America, and everything went crazy.”

Once she had her idea for a schoolboy wizard, Rowling took seven years to finish writing the first book and seeing it published. She said:

“I kept losing hope and putting it away, but that happened less and less as I worked on it. At a certain point it, or I, caught fire, and I stopped doubting. I can remember feeling elated after writing the first Quidditch match, which flowed out of the pen and was barely revised afterwards.”

She said she couldn’t remember a time when she didn’t want to be a writer, and cites the first book that caught her imagination as Busy, Busy World by Richard Scarry, as well as Black Beauty by English novelist Anna Sewell.