Not much information is available about Mary Brown (1929-1999). She lived in Hertfordshire, England and was the author of several novels. These were mostly fantasy, but included at least one historical tale (Playing the Jack) as well. Two children and three cats survive her.
Playing the Jack (1984)
The Unlikely Ones (1986)
The Heart has Its Reasons (1992)
Pigs Don't Fly (1994)
Master of Many Treasures (1995)
Strange Deliverance (1997)
Dragonne's Eg (1999)
There was also a collection published in 1999, titled The Unexpected Dragon, which included Pigs Don't Fly, Master of Many Treasures, and Dragonne's Eg. Most of these works are still in print.
Most of this information taken from http://www.scifibookclub.homestead.com/