James McAvoy revisits his multiple Split personalities in Glass

In M. Night Shyamalan's new superhero thriller Glass, James McAvoy returns as the unforgettable antagonist Kevin Wendell Crumb, a man who suffers from an extreme case of Dissociative Identity Disorder (DID).

It manifests in 24 separate personalities including a violent one known as the Beast, from the film-maker's 2016 movie Split.

Also returning: Bruce Willis as David Dunn and Samuel L. Jackson as Elijah Price/Mr Glass from Shyamalan's 2000 hit Unbreakable.

The writer-director weaves together a story from both these movies involving all his lead characters to form the last in the trilogy.

In our interview at the Crosby Street Hotel in New York City, McAvoy admitted it was the first time he felt starstruck by Willis and Jackson on Glass, which opens here tomorrow.

The 39-year-old Scottish actor said: "I've worked with big movie stars a lot of the time, but usually when you're sharing the screen with them that much, they're your contemporaries.

"So working in that pink room where we did our community therapy session and seeing Bruce and Sam sitting there and my chair is in the middle of them, I'm thinking, 'I'm in pretty incredible company here'.

"You look at Sam and, 'Hi Sam', and then you're like, 'All right Bruce', and they're like, 'Everybody ready?' And you're like, 'Not really'," he said with a laugh.

"I'm pretty much always good between 'action' and 'cut', but it's the feelings before and after that aren't always helpful. Those guys were movie stars and icons when I was a little boy so there's a different relationship and different kind of nerves."

What was it like revisiting the Kevin character?

He is a guy who was abused by his mother and as a result his mind fragmented and dissociated. From that, 23 other people were born.

He is somebody who has been in a kind of coma for large periods of his life while other people are being conscious in his body. He's one of the many that live in the body that used to be just his. Playing Kevin is overwhelming because he finds the whole world overwhelming. He doesn't want to be alive, so it's exceptionally sad playing him.

I don't really feel like I'm playing someone with DID. I feel like I am just playing 20 different individuals who happen to share the same real estate, because if you truly believe that DID exists and is a real thing, you've got to respect that.

What is the particular challenge creating so many personalities?

It's really about time management, because doing prep for that many characters is a lot. But the work is the same work I do when I'm playing any character.

What does this character want? How do they go about getting it? What are the things stopping them from getting it? You do all your background work just like you always do. It's just about trying to do tons of it.

Any favourite personality?

The one I like the most is Patricia because she's got a little bit of kinkiness about her. She's celibate and she'll never have that in her life. She's wedded to her faith, formerly Christianity and latterly the Beast. I think she's always fantasising about being touched.

In this movie, when she first meets Mr Glass, I think she's imagining something happening between them and that's a really fun, sexy thing to play even if the audience doesn't know it. It's just my secret really, but it made her a lot of fun to play.

Were some personalities harder to create than others?

Some of it comes naturally, like Patricia. It was pretty obvious the kind of urban street thing that I wanted to do with Hedwig because I wanted him to appear like he was trying to look like one of the bad boys.

When you've got less to go on with a character, you start to fall back on looking at people you've met in your life. You start to keep an eye on people, you know, those people that you've met throughout your life who've pissed you off and you go, I'm using you. (Laughs.) But you also get people that you've met in your life that you really love and you use them sometimes too.

Physicality was a big part of it. It was important that the audience knows that I'm playing somebody else, even if I'm not saying anything.

Your next film is It: Chapter Two, the sequel to the 2017 horror hit It, where you play the adult version of Bill Denbrough, the former leader of the Losers' Club. Is it going to be scarier?

I think it's going to be a lot scarier because you've got a bunch of adults and you can do weirder things.

There were a lot of moments on set where me and Bill (Hader) and Jessica (Chastain) and (the rest of the cast) were sort of looking at each other and going, 'this is not pleasant... this is not a nice day on set'. It was freaky and what Bill Skarsgard (who plays Pennywise the killer clown) does, it's not just about the make-up or voice, there is an intensity there and he's just really committed to being terrifying.

The writer is the president of the Hollywood Foreign Press Association, a non-profit organisation of entertainment journalists that also organises the annual Golden Globe Awards.