Back when X-Men: First Class was released in 2011, James McAvoy admitted he had no idea how Professor X went bald. Neither did we to be honest.

“He either shaves it or he loses it, I don’t know how they’ll do it,” he said. “In the comic books, he’s still very young when he loses it, on the day his powers activate. We decided not to do that,” he said at the time.

However, now he’s revealed how it happened, putting to bed an age-old comic book mystery. Speaking on The Graham Norton Show, which will air on Friday 27 November, McAvoy said he pulled it out, literally.

“We couldn’t have a superhero just lose his hair so he goes through something so horrible and painful that he literally half pulls his hair out and the rest falls out,” McAvoy explained. Asked if he should have told the audience that he admitted: “I know, Fox Studios that owns me might be angry with me!”

McAvoy is always an open, engaging and entertaining guest to have on the sofa and he doesn’t let fans down this time, also sharing the truth about a rare allergy to horses.

“I’ve had to turn down so many nice jobs because I can’t go near them for too long – it’s a real shame,” he admitted. “I look like I’ve insulted Mike Tyson and my eyes swell up like golf balls.”

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It can also ruin the romance sometimes too, apparently. “I once tried to take Anne-Marie my wife on a romantic ride around Central Park in a carriage and we were in the back and it was freezing so we were given blanket – a blanket that had been used on the horses all day – and I started sneezing and my wife is allergic too so we started wheezing and coughing. It was the most unromantic night of our lives where we were incapable of walking let alone anything else!”

McAvoy can next be seen in Victor Frankenstein alongside Daniel Radcliffe (also on Norton). Watch the actor talk about the movie below: