Keira Knightley is "completely different" when she's with her children

She told Britain's HELLO! magazine: "She incorporates so many personalities within herself and I felt as though they were all true and I felt that in a small way, I understand that - because you're always looking for a character to understand in your own life.

"I think what I understood is; I'm a mother. My identity as a mother and who I am to my kids is obviously very different from who I am in different spaces.

"You know, we're one way to our children. We get into work and we're a completely different way.

"Maybe we have a hedonistic side to us, which you would never show to your kids.

"And Helen is that - it's just in a really, really extreme way. Her other self just happens to be murderous and selling her husband's secrets."

And Keira can understand Helen looking for escapism because becoming a parent can make it easy to lose a sense of self.

She said: "When you become a parent, I think that identity takes over everything for a while, and then, post-that, it's about, 'Who are you within that? And what parts of yourself are you allowed back?'

"So that's what I found so interesting about Helen.

"In part of this story, she's a bored housewife and she wants her other self back, so she explodes her life by having this relationship that she shouldn't be having with this other guy.

"And maybe it's fun for her to feel that other self is alive again?

"I think that's something that parents can identify with, hopefully not in this crazy, extreme way, obviously. I think I connected with that. I recognised that."