Sienna Miller has been showering endless praise on Pirates of the Caribbean star Keira Knightley.

The pair struck up a friendship during the filming of their forthcoming film, The Edge of Love.

She gushed: “I adore her and she is a flawless actress. She works so hard, and she’s so sweet, funny and self-deprecating and kind, and literally…she’ll be a friend for life. I’ll love her until the day I die.”

Speaking at the Glamour Awards, Sienna also said it was nice having a pal to talk about the highs and lows of fame.

She admitted: “There are elements of (fame), whether it seems glamorous from an exterior point of view or not, that are really really hard to deal with.

“And (Keira) is finding it hard, and I’m finding it very hard, and to sit there and be able to talk to each and say ‘yes, this is really difficult and I understand’ is great.”