London, Sep 22 : Actress Dame Helen Mirren admits portraying Queen Elizabeth on stage will be a "challenge" because the role spans 60 years of the monarch's life.

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.

"That'll be a challenge," femalefirst.co.uk quoted Mirren as saying.

However, she thinks the monarch's "unbelievable consistency in everything" will help with the transition, and she is also studying the changes in her speech patterns.

"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," she said.

"I can use all that to signify the age range and we'll come up with other things," she added.

© IANS