The books have sold 80 million copies since Ladybird published the first title in 1964 and are still selling at around 1 million a year, particularly in the Commonwealth.
William Murray's interest in reading began when, after completing National Service, he was appointed to a teaching post in an "approved school". This made him determined to devise a way of bringing literacy to children of all abilities and backgrounds.
With the educational psychologist Joe McNally, he set out to identify the most commonly used words in English. The Key Words books aim to introduce new words gradually, reinforcing learning of core vocabulary by repetition.
Murray's teaching career spanned 35 years and included work in prisons, child guidance clinics, as an adviser for Devon, and in teacher training. He was head of Thirlestaine Court school in Cheltenham between 1960 and 1970. Pupils at the school, which has now closed, are said to have been the models for Peter and Jane.
The books are considered old-fashioned by today's teachers and reading gurus, and it is easy to forget how fresh they seemed to children in the Sixties transferring from the Janet and John scheme. The full-page pictures, with their photographic clarity and wealth of domestic detail, were peculiarly fascinating to very young children.
The text itself, while making no pretensions to plot or characterisation, also had a hypnotic simplicity: "We like to play. Come play with us. Peter has a ball. Jane has a doll."
Poor Jane, of course, would not pass muster as a role model today. Usually shown wearing a spotless white dress with matching ankle socks and hairband, she was perpetually "looking on" while Peter climbed trees and helped Dad with his DIY.
Liz Waterland, now the most popular reading guru in teacher training, said that Peter and Jane have been considered out of date for some time. "They were effective in their day," she said, "but there's no story, just a series of incidents written around the key words; the social situations are dated. "
However, they are still being used by some parents - including, apparently, Richard Branson.
William Murray retained an active interest in his books after he retired, and was busy revising and proof-reading up to his death, according to Mike Gabb, publishing director at Ladybird. "Those of us who worked with him in his last months were not aware of his illness. He continued to offer a unique insight into the ways in which children acquire reading skills."