James McAvoy didn't realise that 'Split' was a sequel to 'Unbreakable' when he was shooting the movie.

The 39-year-old actor played multiple-personality sufferer Kevin Wendell Crumb in M. Night Shyamalan's 2016 psychological thriller 'Split' - a man who has 24 different personalities and kidnaps three teenage girls whilst moving towards becoming his darkest alter ego The Beast.

McAvoy reprises his role in new film 'Glass' - which completes the trilogy which began with 'Unbreakable' - but he has now confessed that it took him a ''few weeks'' to realise that 'Split' was a follow-up to the 2000 hit film, which starred Bruce Willis and Samuel L. Jackson.

In an interview with website DigitalSpy, he said: ''I read the first version of 'Split' that I got sent and there was a little tenuous clue there - if I had been sharper eyed, I'd have seen it, but I missed it. I got into rehearsals and he kept talking about 'Unbreakable'. And then it became clear, it dawned on me, the veil was lifted and I was like, 'Oh my God'. Then a few weeks after that, I came clean with him and I was like, 'Dude, I did not get that at all.' I think he realised that the little clue he was giving everybody just needed to be amped up and he ended up coming up with a really cool scene at the end as well.''

Despite it taking McAvoy a while to come to understand with his director was doing, it was always Shyamalan's plan to link the Scottish actor's alter ego Kevin Wendell Crumb to Willis' super strong character David Dunn and Elijah Price, played by Jackson.

The director previously said: ''It always evolves a little bit. Essentially, it was this. It was this guy going to fight this guy to prove this guy's theory. These three were always tied in that triangle.''