Writer Mary Hayley Bell has passed away at the age of 91.

The author was best known for Whistle Down The Wind and her marriage to famous actor John Mills. Her book, written in 1958, was filmed in 1961 and adapted by Andrew Lloyd Webber in 1998 into a successful West End musical.

Bell was also a prolific playwright and film writer, with plays including Duet for Two Hands and The Uninvited.

Bell had suffered from Alzheimer's for many years and was wheelchair-bound. She passed away on December 1.