Hollywood actress Keira Knightley is happier than she has ever been, and it's all down to her cool mother.

The British PIRATES OF THE CARIBBEAN star insists being able to talk openly about sex and smoke roll-ups with her mother has made her a more positive and bubbly person.

She says, "When I was a child my mother and I would always talk about sex.

"She's come up to my room and have me roll cigarettes for her and then tell me I had to have one with her.

"She's the perfect mum."