Sally has had a great many roles in the theatre as well as in TV and film productions. She is perhaps best known as Irma Pince the librarian at Hogwarts. There is a theory that Irma Pince, the librarian during Harry Potter’s years at Hogwarts, is actually Severus Snape’s mother Eileen Prince in disguise. Pince’s name is an anagram of “I am Prince” or “I’m a Prince”. Her description matches that of Eileen’s, having the same hooked nose and dark hair as Severus.