The 67-year-old- who has previously played the monarch in hit movie 'The Queen' - is to star in 'The Audience' in London's West End next year, reported Contactmusic.
"That'll be a challenge. Her voice has changed and I can use that - she had a terribly posh voice when she was young. But now even the queen, while she isn't quite dropping the ends of her lines - though her grandsons do - there's a tiny bit of estuary creeping in there. I can use all that to signify the age range and we'll come up with other things," she said.
'The Audience' examines the relationship between the queen and her Prime Ministers.