Twilight director Catherine Hardwicke knew she'd found her Bella Swan and Edward Cullen for the vampire romance when Robert Pattinson and Kristen Stewart first met.

The filmmaker cast Stewart as Bella after falling in love with her Into the Wild character Tracy Tatro, but she tells PopSugar she knew finding Cullen would be a lot more difficult.

Hardwicke flirted with the idea of casting future Fifty Shades of Grey star Jamie Dornan and Jackson Rathbone, who eventually landed the role of Cullen's brother Jasper, but reveals she wanted someone who looked "otherworldly".

"That was the biggest challenge because he (Edward) is just a magnum supernatural character," Hardwicke explained in a new interview to mark the 10th anniversary of the original Twilight movie.

"But you've got to believe he can still be in high school, and that's a very small category." Hardwicke reveals she narrowed her search down to four people, and Robert eventually won the role after a chemistry read with Stewart, who was to become his girlfriend in real life.

"We did the auditions at my house, the chemistry read, because it was so important to me that Kristen really felt something for this person," the director told the outlet.

"It wasn't all going to be fake or miserable for her.

I wanted it to be a real chemistry there.

And at the end of that day, it was like, 'It's got to be Rob!'" The Twilight films will return to cinemas next month (Oct18) to mark the 10th anniversary, while bosses at Fathom Events and Lionsgate's Summit Entertainment are inviting fans to return to Forks, Washington, where the films were set, for a special screening of the first movie and the debut of Twilight Tour...

10 Years Later, which will feature on the upcoming Twilight 4K Ultra HD home entertainment release.

Hardwicke will introduce the screening.