In 2005 she starred in a West End production, playing Celia in As You Like It alongside Helen McCrory as Rosalind. Two days after it opened, McCrory was taken ill. Miller overstepped the understudy and texted the director David Lan: 'I know Rosalind's part if you need me to do it. X.' It was an audacious display of ambition that paid off. She only needed two prompts during her performance of Shakespeare's longest female role and it won her a standing ovation.
Why had she learnt the leading role? 'I hadn't tried to, but it had been eight weeks and I've got a weird memory for lines. Also, watching Helen McCrory, who's this incredible actress, every day, I was far more interested in her performance than my own. Then you've got the Tannoy on in your dressing-room so you're hearing these lines. I suddenly realised that I knew it. But I knew Dominic West's part [Orlando] as well.'
http://www.telegraph.co.uk/culture/film/3553887/Sienna-Miller-a-sense-of-theatre.html
"The gods who nurse this universe think little of mortals' cares. They sit in crowds on exclusive clouds and laugh at our love affairs. I might have had a real romance if they'd given me a chance. I loved him, but he didn't love me. I wanted him, but he didn't want me. Then the gods had a spree and indulged in another whim. Now he loves me, but I don't love him." - Cole Porter