Daniel Radcliffe reveals his one bug bear about 'Harry Potter'

The Harry Potter cast has reunited for the Harry Potter 20th Anniversary: Return to Hogwarts, and in sneak peeks of the reunion Daniel Radcliffe, Emma Watson and Rupert Grint have shared some secrets about filming the hit series.

The trio first appeared in the Harry Potter franchise back in 2001, up until Harry Potter and The Deathly Hallows Part 2 in 2011.

While filming the sequels the entire cast watched one another grow up, and while the whole cast hold a soft spot in their hearts for the movie for many years to come, Daniel, 32, who played the titular character, had one pet peeve.

In a snippet of the reunion special ahead of the January 1, 2022 release, Daniel shared his annoyance at having to let his hair grow over the summer months, and in the breaks between filming.

He shared: ''I'll always be happy to talk about it. I think people expect me not to want to talk about it. But that's like somebody never talking about their childhood or teenage years.

'Every part of my life is connected to Potter and to Leavesden. My first kiss is connected to someone here, my first girlfriends were here... everything I can think of is that related right now. It all spirals out from the Potter set somewhere.

'My one bone to pick with Mike Newell, is that every year when we left for the film, we finished a film, they said "don't cut your hair over the summer, we'll cut it when you get back, and we'll decide what they want to do.'

Despite holding off on any visits to the barbers, Daniel was left disappointed when the film director, Mike Newell, was happy to leave their hair long and scruffy when they returned to filming.

He continued: 'And me and Rupert both dutifully grew our hair for months, and then came in and he was like: "Great!"

'And we went: "No, no no no no. You're not leaving us like this? We're supposed to be becoming teenagers and dating girls in this film. Like, you can't? That's not what it's gonna be is it?"

'So I think we were pretty devastated as we realised that it was. But still, I still love the man!'

Although the cast have insisted it feels like 'no time has passed' when the film debuted 20 years ago, Emma Watson - who plays Hermione Granger - was nervous about the reunion.

Emma, 31, said: 'You know, some of us haven't seen each other for years, and so it's just been a joy, an unexpected joy.

'I really didn't know how it would feel. I felt quite overwhelmed this morning and then I've just been really pleasantly surprised by just getting to relive it all.'

The Harry Potter 20th Anniversary: Return to Hogwarts reunion will hit screens on January 1, 2022, and will air on HBO Max, Sky and NOW in the UK.