Ian McKellen has enjoyed a successful run playing the mutant master of magnetism, Magneto, in Fox’s X-Men film franchise for the past 15 years. So what possessed the storied English actor to play a supervillain in a Hollywood franchise, especially after the decline of the Batman movies had attached such a stigma to superhero movies as a genre?

Speaking to UPROXX, McKellen says it has to do with the core concept behind the X-Men, and the different level of commitment involved in signing up for such a film back then.

Well, [director Bryan Singer] persuaded me. X-Men was about something. Superman isn’t really about anything. It’s a joke. The nerd changes his underpants and becomes a Superman. That’s James Bond: “Shaken, not stirred,” silly, stupid, British twit… and then, Action Man! But X-Men is about the problems of being a mutant. And we’ve all felt we’re mutants on occasion. So, that was the hook for me. And don’t forget, I didn’t have to sign to do any more than one; I’m just doing a movie.

This explanation is in line with previous statements by McKellen, where he described X-Men movies as “superior.”

McKellen’s next film is Mr. Holmes, opening in theaters in the United States on July 17.