"I just thought I fitted the description of the character in the book - a bit small and mad," says Hugh Mitchell.
His inkling triggered a magical story, because director, Chris Columbus, agreed and chose Hugh (13) to play little Colin Creevey, amateur photographer and Harry's hero-worshipper, in Harry Potter and the Chamber of Secrets.
Hugh, a pupil at Pilgrims' School, Winchester, was picked from thousands for the role of Colin, who starts his first year at Hogwarts School in the second Harry Potter book.
Last week, the entire school got the morning off to watch their classmate in a special showing at The Screen, in Southgate Street.
Hugh says he's even received three fan letters since the film went out. But the modest teenager had never acted before and says he was stunned when he landed the part.
Hi's father, Philip Mitchell, head of maths at Pilgrims', recalled how his resourceful son went about the application. "The nice thing is that it was entirely off his own back.
"A poster went up towards the end of the summer term in 2001. I hadn't taken any notice until I came home to find Hugh at the computer. He said he was writing to a casting director in London. We warned him it would be one of 10,000 and thought nothing more about it."
But the letter led to auditions and a meeting with the director and producer at Warner Bros. "At this point, minds started to be concentrated," said Mr Mitchell.
They found out the part of Colin was the last to be cast, as the numbers whittled down to five, then two. Hugh was at school when his mum, Anne, came in to tell him a letter had arrived, saying he had the part. "I was really excited, but also half scared," he said.
Filming started about 10 days after he was told last November. "I first met everyone when we read through the script," said Hugh.
"It was really surreal meeting all the famous people. I talked to Alan Rickman and he was really nice, a bit shy."
Hugh says it was hard to remember all the lines, but he was not too nervous. "I just had to get into character of being as annoying as possible," he joked.
But his role involved more than simple acting. In part of the film, Colin Creevey is petrified, turned to stone by the stare of a giant snake living in a hidden cave at the school.
"In effect they made a body cast of me," explained Hugh. "They made all the different parts and fitted them together. They took pictures of my eyes and compared my skin to make sure it was right.
"It was really strange when I stood next to the finished statue. We were so alike people couldn't tell which was real."
Fame doesn't seem to have gone to Hugh's head. He says school mates bombarded him with questions about filming. "I don't mind. They're not jealous or anything like that."
He says he preferred seeing the film with friends in Winchester to the glamour of the London premires.
His father said Warner Bros had made careful rules about Hugh's film earnings and it was being saved. "It will be a nice nest egg, probably allowing him to leave university without any student debts."
The part has opened up other roles and Hugh now has a London agent. In January, he will also be appearing in a two-part ITV drama with ex-Heartbeat star, Niamh Cusack.
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