Who's the woman behind Mary Poppins?

Mary Poppins Returns will be hitting the big screen next week following its European premiere at the Royal Albert Hall.

It is the sequel to the original film, which came out in 1964 and was a story about a magical nanny who helps care for the Banks family's two children, Michael and Jane, in Edwardian London in 1910.

This follow-on, decades after her original visit, sees Mary return to help the now grown-up Banks siblings, and Michael's children, through a difficult time in their lives.

But what about the woman behind the story?