"I really kept my distance and I was aware. It was kinda half-hearted, 'cause I was going like, 'What am I...if she turns around, is she gonna notice?'" Dornan said. "She got off a few stops earlier than I was planning so I was like, 'Alright, I'll have to commit to this here.'"

The actor said he followed the woman around several street corners and then thought, "'What are you doing?'"

"It felt kind of exciting, in a really, like, sort of dirty way, and I'm sort of not proud of myself," he said. "But I do honestly think I learned something from it, just 'cause I've obviously never done anything like that in my life, so it was intriguing and interesting to sort of enter that process of like, 'What are you following her for?' and 'What are you trying to find out?'"

"So it was interesting, but no, I actually tried to have a lot of fun on set," he added. "I don't think it's healthy to stay in the headspace of someone who is as evil as he is."