LOS ANGELES (REUTERS) - 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 (Nov 16).

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 them, 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 Jan 1 on streaming platform HBO Max. It premieres in Singapore on the same day on HBO Go. Warner Bros and HBO are owned by AT&T.

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 Britain) released in November 2001.

The film franchise based on JK Rowling's stories about an orphaned boy with magical powers took in some US$7.8 billion (S$10 billion) at the global box office.

The 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.