Sienna Miller and Tom Sturridge are still "best friends"

However, despite their closeness, the 35-year-old actress admits things are "complicated" between herself and her ex-partner.

She told Allure magazine: "We do bedtime every day. We felt like as much togetherness as possible would be ideal, and fortunately we really love each other and are best friends, and so that works.

"It's not that it's not complicated, because it is."

Though the 'Lost City of Z' star adores being a mother, she admits being responsible for a child can sometimes feel "crippling", especially when she looks at other people in different situations.

She said: "You're so enriched by it and so fulfilled, but at the same time, I look at these people who just don't have any responsibility, and it feels like the responsibility is crippling."

And despite her glamorous image, Sienna is all too aware of the sometimes harsh realities of parenthood.

She said: "I had an amazing moment the other day where I just heard this 'Mama!' from upstairs.

"I said, 'I'm coming, I'm coming.' And as I got to the landing I just smelled, like, puke. And she'd thrown up basically off the top bunk, so the splatters were like, Pow! Like all four walls. She had the norovirus or whatever.

"And I skidded on the sick and fell. Whacked my head. Then I get her out of the bunk; she's crying, covered in sick. I take her to the bathroom, take all her clothes off, and then the dog comes up and starts eating the sick.

"And I get her in the bath and in my bed, and I'm just, like, literally naked, mopping, and crying at midnight. You know, and that's parenthood."