In 1958 she started working for the Indian philosopher Krishnamurti and remained for nearly twenty years.
Mary Cadogan's writing career started late but her first book You're a Brick, Angela! was an immediate success.
Her articles on the history of children's fiction have appeared in a number of magazines.
She wrote a notable biography of Richmal Crompton, who wrote the Just William books.
She first met her in the late 1940s, but reported that she was then too shy to ask any questions about her writings.
She was editor of the Just William Society magazine for many years and also edited the Story Paper Collectors' Digest between 1987 and 2005.
She was also a member of The London Old Boys' Book Club.
Her books, including her collaborations with Patricia Craig, have covered a wide spectrum of popular fiction.
She was interviewed for Gyles Brandreth's programme on the centenary of Billy Bunter that was broadcast on BBC Radio 4 in February 2008, and received an Honorary Doctor of Letters from Lancaster University in 2009.
Currently has a 5 star carrot cake recipe on BBC good food, with over 1500 reviews.
Cadogan died on 29 September 2014.