JK Rowling says that “girls are very apt to romanticise” the antihero, and reveals that she had been forced to pour “cold common sense” on the startling number of readers who fall for the arrogant, unscrupulous bully Draco Malfoy in her Harry Potter books.

Rowling has been providing new snippets about the world of Harry Potter on her website Pottermore for the past 10 days, giving fans insights into everything from a “ghost” storyline that she didn’t include in the final story, to the history of the Leaky Cauldron pub. She has now unveiled her lengthiest piece of writing yet, offering a glimpse into the future of Harry Potter’s arch enemy Draco, and her own thoughts on the character.

“Draco remains a person of dubious morality in the seven published books, and I have often had cause to remark on how unnerved I have been by the number of girls who fell for this particular fictional character,” writes Rowling, with a nod to the actor Tom Felton, “who plays Draco brilliantly in the films and, ironically, is about the nicest person you could meet”.

‘About the nicest person you could meet’ … Tom Felton who plays Draco Malfoy in the Harry Potter films. Photograph: Jaap Buitendjik

“Draco,” writes Rowling, “has all the dark glamour of the anti-hero; girls are very apt to romanticise such people. All of this left me in the unenviable position of pouring cold common sense on ardent readers’ daydreams, as I told them, rather severely, that Draco was not concealing a heart of gold under all that sneering and prejudice and that no, he and Harry were not destined to end up best friends.”

The novelist also reveals her thoughts about Draco’s future. She has imagined that the character “grew up to lead a modified version of his father’s existence; independently wealthy, without any need to work, Draco inhabits Malfoy Manor with his wife and son [Scorpius].” He is married to the younger sister of a fellow Slytherin, Astoria Greengrass, who Rowling says “had gone through a similar (though less violent and frightening) conversion from pure-blood ideals to a more tolerant life view”, and who is felt by Draco’s parents Narcissa and Lucius “to be something of a disappointment as a daughter-in-law”.

“As Astoria refused to raise their grandson Scorpius in the belief that Muggles were scum, family gatherings were often fraught with tension,” writes the novelist, also expanding on her belief that the character of Draco has a “dual nature”.

“His strange interest in alchemical manuscripts, from which he never attempts to make a Philosopher’s Stone, hints at a wish for something other than wealth, perhaps even the wish to be a better man. I have high hopes that he will raise Scorpius to be a much kinder and more tolerant Malfoy than he was in his own youth,” she writes, ending: “His Christian name comes from a constellation – the dragon – and yet his wand core is of unicorn. This was symbolic. There is, after all – and at the risk of re-kindling unhealthy fantasies – some unextinguished good at the heart of Draco.”