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Harry Potter stars Daniel Radcliffe, Emma Watson and Rupert Grint are reuniting with other cast members from the blockbuster film franchise for a special 20th anniversary TV retrospective, movie studio Warner Bros said on Tuesday.

But Harry Potter author JK Rowling will not be among those making a personal appearance on the show.

Robbie Coltrane, who played Hagrid, Tom Felton (Draco Malfoy), Helena Bonham Carter (Bellatrix Lestrange), Gary Oldman (Sirius Black), director Chris Columbus and other stars of the eight movies will join the former child actors for Harry Potter 20th Anniversary: Return to Hogwarts on the movie set in London where the first film was made.

The special will be broadcast on January 1 on streaming platform HBO Max.

The retrospective will see the cast return to the original Hogwarts boarding school sets that were featured in the first film Harry Potter and the Sorcerer's Stone (Philosopher's Stone in the UK) released in November 2001.

The film franchise based on Rowling's stories about an orphaned boy with magical powers took in some $7.8 billion at the global box office.

Rowling's name was not included in the announcement on Tuesday but she will feature in archive footage that will be shown in the special, a source familiar with the matter said.

Rowling's opinions on transgender issues in the last year have been a cause of controversy, with some in the LGBTQ community accusing her of transphobia.

The TV special is one of several 20th anniversary events planned by Warner Bros, including a TV quiz contest for Potter fans hosted by Helen Mirren, which will include cameo appearances by some of the cast and celebrity fans including comedians Pete Davidson and Jay Leno.