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The three-hour walking tour's attractions include the original Great Hall of Hogwarts School, built for Harry Potter And The Philosopher's Stone.
Tom Felton, who played Draco Malfoy, said:
"I will never forget walking through the Great Hall for the first time. It was just as magical now as it was."
Hundreds of screaming Potter fans queued outside the studios in Leavesden, near Watford in Herts, where all the multimillion pound-grossing films based on JK Rowling's magical stories were shot.
Local boy Grint, who played Ron Weasley, said: "This is the most glamorous I've ever seen Watford."
Harry Potter stars turned out at the red carpet opening of a studio tour which gives fans a behind-the-scenes glimpse of the blockbuster films.
Rupert Grint, Tom Felton and Bonnie Wright were among actors at the grand opening of the Warner Brothers Studio Tour - The Making of Harry Potter.
Latest ITV News reports
'Warner Bros' Studio Tour London - The Making of Harry Potter' opens today ending months of waiting for Potter fans across the world.