That was over 54 years ago in 1967.
Today she is 76, and has starred in 115 movies in total, 112 since Herostratus was released.
In Herostratus, I think Helen Mirren looks:
Herostratus scores 5.9 out of 10 on The Movie Database.
Helen Mirren's first acting role was as 'Advert Woman' in Herostratus, released in 1967 when she was 21.