Daniel Radcliffe, Rupert Grint and Emma Watson are back together in first look at Harry Potter reunion

And of course, we hear the main trio talking about their time working on the films. "It feels like no time has passed, and loads of time has passed," Watson says, with Grint adding, "This is the perfect time to sit down with everyone and reminisce."

Radcliffe then says: "The thing that scared me the most was the implication that the most meaningful thing in our life was done, and there's something so joyous about seeing everyone and be like, 'It wasn't though.'"

We also hear from several other big names, including Bellatrix Lestrange actor Helena Bonham Carter, who reveals: "One of the highlights of my part was when I had to pretend to be Hermione pretending to be Bellatrix. I've still got the teeth actually!"

Meanwhile Ralph Fiennes – who famously played the role of archvillain Voldemort – says: "My sister has children who were then around 10, 11, 12. And I said, Martha I don't know about this Voldemort. [She said] 'What, you're being asked to play Voldemort? You've got to do it!'"

The clip also features several snippets of footage from the films and closes with Grint declaring: "It's a strong bond that we'll always have. We're family, and we'll always be part of each other's lives."

The reunion special, titled Return to Hogwarts, was confirmed by HBO Max last month – and will air exclusively on Sky and NOW in the UK on New Year's Day.

HBO Max has described the event as seeking to “tell an enchanting making-of story through all-new, in-depth interviews and cast conversations” with other names set to appear including Gary Oldman, Imelda Staunton, James and Oliver Phelps, Mark Williams, Robbie Coltrane, Jason Isaacs, Ian Hart, Alfred Enoch, Evanna Lynch and director Christopher Columbus.

In a statement, Tom Ascheim, president of Warner Bros Global Kids, Young Adults and Classics, said: “This retrospective is a tribute to everyone whose lives were touched by this cultural phenomenon — from the talented cast and crew who poured their heart and soul into this extraordinary film franchise to the passionate fans who continue to keep the Wizarding World spirit alive 20 years later.”

Harry Potter 20th Anniversary: Return to Hogwarts arrives on HBO Max in the US and on Sky and NOW in the UK on 1st January 2022. Looking for something to watch? Check out our TV Guide.

This year’s Radio Times Christmas double issue is on sale now, featuring two weeks of TV, film and radio listings, reviews, features and interviews with the stars.