Emma Watson has said filming Harry Potter 20th Anniversary: Return To Hogwarts was “an unexpected joy”.

READ MORE: Harry Potter & The Cursed Movie: how Fantastic Beasts: The Crimes Of Grindelwald became JK Rowling’s most controversial film

Return To Hogwarts will see Watson, who played Hermione Granger in the eight-film franchise, reunite with co-stars Rupert Grint (Ron Weasley) Daniel Radcliffe (Harry Potter) and other cast members to celebrate the 20th anniversary of the first film, Harry Potter And The Philosopher’s Stone.

In a new clip from the special, Watson said: “I honestly didn’t know how I was going to feel this morning. Then something happened where it was the comfort of the people that I’ve known for such a long time, and the history that we share, and that sense of safety. Then once I started feeling really safe, just enjoying everything that we made and we created and feeling like we could really celebrate and just enjoy being together.”

She continued: “Some of us haven’t seen each other for years. It’s been a joy. An unexpected joy.”

Watson then went on to admit she felt “overwhelmed” ahead of filming the special, and added “I’ve just been very pleasantly surprised by getting to relive it all.”

Elsewhere in the clip, Radcliffe spoke about his relationship with nostalgia. “It’s been lovely to see everyone and I didn’t know if it would be, because I have a very mixed relationship with nostalgia. It’s so much feeling, it can be weirdly painful sometimes.”

However, he added that “the thing that scared me the most when we were coming out of it, was the implication that the most meaningful thing in our life was done. There’s something so joyous about seeing everyone and being like ‘it wasn’t, though’. We’ve all gone on to do other stuff. People have wives and kids and lives, there’s something really lovely about seeing that.”

Harry Potter 20th Anniversary: Return To Hogwarts premieres January 1, 2022 on HBO Max in the US and Sky/NOW TV in the UK.

Directors across all eight films will make appearances, including Chris Columbus, Alfonso Cuarón, Mike Newell and David Yates, alongside producer David Heyman.

Other cast members featured include Robbie Coltrane, Helena Bonham Carter, Ralph Fiennes, Jason Isaacs, Gary Oldman, Imelda Staunton, Tom Felton, James Phelps, Oliver Phelps, Mark Williams, Bonnie Wright, Toby Jones, Alfred Enoch, Matthew Lewis, Evanna Lynch, Helena Bonham Carter and Ian Hart.