Rowling's most famous character, Harry Potter.

LONDON - The author of the best-selling Harry Potter books revealed for the first time yesterday the identities of the people who inspired her characters, including the childhood friend whose antics bore startling similarities to those of the fictional schoolboy wizard.

Ian Potter, a construction worker who, as a child, had a "thing about slugs" and sabotaged the training wheels on his sister's bicycle, lived just four doors away from J.K. Rowling as she was growing up in the village of Winterbourne, near Bristol.

Dressing up as wizards and witches, concocting fantasy potions and telling stories were just a few of the games Rowling played as a child with Ian Potter and his little sister Vikki.

Mr. Potter admitted that he was a mischievous boy who loved playing pranks.

"The girls, including Joanne, used to dress up as witches all the time," said Mr. Potter, 43, who lives in Yate, near Bristol.

"And the boys, obviously, would be wizards.

"I was one for tricks, especially in my younger days.

"I used to get my sister and Joanne to go in for me and ask my parents if I could stay out a bit later."

More than 30 million Harry Potter books have been sold worldwide since 1997 and Harry Potter and the Goblet of Fire, the fourth in a series of seven books, will be published next week with a print run of one million copies.

The Hollywood film Harry Potter and the Sorcerer's Stone is expected to be released in November, 2001.

Mr. Potter, whose two daughters, Charlotte, nine, and Shannon, five, are both Harry Potter fans, said he felt privileged to have played a role in the creation of the childhood hero. Vikki Potter, his younger sister, described how he was always getting into mischief in a similar way to the fun-loving trainee wizard, Harry.

"Ian was the perfect inspiration for the mischief-making wizard character," said Miss Potter, 32, of Chipping Sodbury.

"He was a total nightmare, a real horror. He used to do things like booby-trapping the stabilizers [training wheels] on my bike, collecting tadpoles in jars and then plastering the green slime everywhere. He had this thing about slugs."

Miss Potter, a sales director at a software company, also recalled how Rowling would make potions and read stories as part of their fantasy games. "I think it's mad to have a hero called Potter, but that's typical of Joanne," she said.

"We were forever dressing up. Our favourite thing to dress up as was witches. We used to dress up and play witches all the time. My brother would dress up as a wizard.

"Joanne was always reading to us. She used to read things like poetry, and we would make secret potions for her. She would always send us off to get twigs for the potions."

Cantankerous Aunt Marge, the overweight relative who keeps bulldogs, was based on Rowling's maternal grandmother, Frieda, who preferred "her dogs to human relatives," according to the author.

The inspiration for Professor Snape, the spine-chilling teacher at Hogwarts School of Witchcraft and Wizardry, who made Harry's life a misery, was drawn from a teacher at Rowling's former school -- although she declined to name him.

The character of Ron Weasley, one of Harry's best friends, who comes from a poor but loveable family, was based on Rowling's oldest friend, Sean. His full identity remains hidden.

Harry's other best friend, Hermione, the studious and courageous book-lover described by Rowling as the "most brilliant" of the three friends, is the author as a young girl.

Rowling's grandmother, Frieda, who inspired Aunt Marge, was illegitimate, born of Scottish parents. She was abandoned in a London nursing home, whose owners adopted her.