Sir Ian McKellen on filming the final Hobbit film: “I had no idea what I was doing"

“The best thing about having now seen the movie is understanding the plot,” he tells Graham Norton of his final turn as the wizard Gandalf. “I had no idea what I was doing during filming.”

It’s a film which – and the clue is in the name here – ends with a huge battle scene. “They are amazing,” McKellen says of the dramatic fights, but adds, “Don’t ask me any more about how it is done, as I don’t really understand it.”

Indeed, it’s no secret McKellen didn’t enjoy some of the more technical sides of the shoot, particularly green screen work, which separated him from the rest of the cast.

“Some of it was really exciting, like filming on a mountain top. But filming with a green screen is the miserable part. At the end of the day, I shed a tear with my head in my hand and said, ‘This is not why I became an actor,’ forgetting the microphones were still on!” he reveals.

However, having attended the premiere in London at the start of the week, the actor says it’s “very moving” to see kids sleeping out all night to get a glimpse of the cast.

“These people were not born when we started making Lord of the Rings and it’s a big part of their lives. It’s not the end for them because they will now be able to see all six films and show them to their kids.

“We’ve made classics and that’s lovely.”

The Hobbit: The Battle of the Five Armies is in cinemas from 12th December 2014.

Watch The Graham Norton Show tonight at 10:35pm on BBC1