Sean Connery turned down the role of Gandalf in hit movie franchise Lord of the Rings. Gandalf is played by Ian McKellen. (Reuters/Handout)

Sean Connery turned down the role of Gandalf in hit movie franchise Lord of the Rings because he didn't understand the part.

Despite being offered a large salary and a portion of the box office profits for the part of the wizard in the film trilogy, which has so far earned over $2.9 billion worldwide, Connery gave up the role, according to BusinessStandard.com, allowing Sir Ian McKellen to grab it.

The films were considered a risky undertaking at the time by Time Warner's movie studio New Line Cinema as they were being shot by a relatively then-unknown Peter Jackson, and with no Hollywood big names on the bill.

Brian Warner of Celebritynetworth.com says, "Even a veteran star like Sean can make a mistake so big that it causes him to lose out on a mind-blowing amount of money. In order to convince Connery to sign on to the film, the producers pulled out all the stops.

"In addition to a $10 million per film salary, they offered Connery 15% of the box office for all three movies. In what would turn out to be a monumentally poor decision, Connery declined the part because he "did not understand the script".

Connery said of the part, "I never understood it. I read the book. I read the script. I saw the movie. I still don't understand it. Ian McKellen, I believe, is marvellous in it."