First look at Harry Potter reunion: Watch as Daniel Radcliffe, Emma Watson and Rupert Grint return to Hogwarts

Rupert Grint, Emma Watson and Daniel Radcliffe star during the Harry Potter reunion. Photo / HBO Max

Daniel Radcliffe, Rupert Grint, and Emma Watson were just children when they starred in the first Harry Potter film. Now 20 years on they have reunited.

The franchise catapulted the three child actors to fame and now the cast have got together to reminisce about their time playing the iconic characters,

Harry Potter 20th Anniversary: Return to Hogwarts will air in the New Year, and features almost every cast member you can imagine.

Helena Bonham Carter (Bellatrix Lestrange), Tom Felton (Draco Malfoy), Evanna Lynch (Luna Lovegood), James Phelps (Fred Weasley), Oliver Phelps (George Weasley), Bonnie Wright (Ginny Weasley), Matthew Lewis (Neville Longbottom), Gary Oldman (Sirius Black), Jason Isaacs, and Robbie Coltrane are just some of the stars who feature in the reunion special.

"It feels like no time has passed and loads of time has passed," Emma Watson says in the trailer.

"The thing that scared me the most was the implication that the most meaningful thing in our life was done," Radcliffe says.

"And there's something so joyous about seeing everyone and being like, it wasn't though."

Leave it to Ron Weasley (Rupert Grint) to deliver a tear-jerking line that could send Harry Potter fans into an emotional spiral:

"We're family," he says.

"We'll always be part of each other's lives."

While there is almost every cast member you can think of featured in the reunion teaser there is one notable absence - the author of the Harry Potter series J.K. Rowling.

It is thought she did not join the cast because of her comments directed at the transgender community.

In 2020, Rowling aired a number of unfounded claims on her social media about transgender hormone therapy and took offence to the term "people who menstruate".

Her comments sparked a backlash from Harry Potter fans, LGBTQ organisations and even Harry Potter stars themselves.

The return to Hogwarts special will "tell an enchanting making-of story through all-new, in-depth interviews and cast conversation", according to the synopsis from HBO Max.

Watch the Return to Hogwarts trailer above.

• The Harry Potter reunion special airs on TVNZ 2 on January 2, 2022.