Warwick Davis has admitted he was “terrified” the first day on set for the new Harry Potter TV series.

The 56-year-old played Hogwarts charms professor Filius Flitwick in all eight of the Harry Potter movies.

He is so far the only cast member from the original films to reprise their role for the upcoming HBO series, which will premiere on Christmas Day.

On Wednesday, the actor made an appearance at the opening of the new UK Harry Potter flagship store on Oxford Street.

Speaking to the Press Association at the event, Davis explained his initial nerves at returning to the franchise.

He said: “It was slightly daunting to come back and play, even though I was playing the same character once again in the HBO series.

“I wanted to make sure that this version of Flitwick was slightly different. My first day on set was terrifying because I was like, ‘Am I going to do this? Can I still do this in the way that I could?’” he said.

However, he added: “I felt really honoured to have been asked to kind of step back into those famous wizard’s shoes once again. It was just a lovely experience to be back and to kind of see the world slightly reimagined.”

When asked if he felt any responsibility to the new cast members, Davis said: “They all looked to me because I’ve been there before and done most of the stuff before.”

But he said the only advice he gave them was to “fully immerse themselves in this world”.

“They have to believe that they’re a Hogwarts, because if they believe it, the audience will believe we’re there as well. You know, that’s the same when you do anything with special effects, anything like Star Wars. You have to believe that what you’re seeing is there, and you are there, and you are a wizard,” he said.

Davis admitted that it was also emotional returning to the world of Harry Potter.

“When I put the new outfit on that I wear in the series, it was quite emotional. Looking in the mirror for the first time and knowing that I’ll be doing this for the next 10 years as well is actually a wonderful kind of thing to think about because he is a character that’s very close to my heart,” he said.

Davis said he approached the role slightly differently this time around, explaining Flitwick now felt “fresher and more vibrant”.

“He’s a little cheekier but at the same time, in the back of my mind, I always remember he is an expert in what he does, so I made sure I kept that kind of integrity in him as well. That’s a more solid thing that I have with the character this time.”

Ahead of the series launching on Christmas Day, Davis said he hoped fans were satisfied.

“I’m just a cast member, but I’ve nurtured this project for the last year and a half and not talked about it. And now we’re going to suddenly release all of the secrets to the world, and hope they like it,” he said.

“It’s a great responsibility to bring these characters to the screen again from the books, as it was with the films, so we just hope all of us, the cast, that we’ve done a good job and do justice to those characters.”

The new Harry Potter flagship store opened its doors on Wednesday, with Davis saying its size left him in “awe”.

“People have been lined up all night to be the first ones through those doors and see what we have in store here. It means a lot. After all these years, as well, there’s still as much enthusiasm for Harry Potter as there once was,” he said.

“I think what it is about Harry Potter. Everyone likes to believe there is a bit of magic to be found. I mean, we’re lacking magic in the world right now. So, you can come to this shop and you can be immersed in magic once again, which is lovely. It’s what we all need right now.”

During the store’s opening, transgender rights protesters gathered outside the store over Harry Potter author JK Rowling’s vocal stance on gender identity.

A group of protesters were heard shouting: “Trans rights are under attack. What do we do? Stand up fight back.”

Rowling previously stated she thinks biological sex is “real” and “immutable” and has also been critical of self-declared gender identity, calling it “quasi-religious” and “anti-science”.

She has denied being transphobic and previously said she respects “every trans person’s right to live any way that feels authentic and comfortable to them”.

The first season of the HBO show will launch this Christmas and has been adapted from Rowling’s first novel, Harry Potter And The Philosopher’s Stone.

The three main characters are young wizards Harry Potter, Ron Weasley and Hermione Granger, played by Dominic McLaughlin, Alastair Stout and Arabella Stanton.

The show aims to be a faithful adaptation of Rowling’s novels while providing a wider insight into the magical wizarding world beyond that was depicted in the hit film franchise, which ran from 2001 to 2011.