GENES have a wayward, as well as a selfish, disposition. At the end of the 19th century Charles Cannan — double first at Oxford, Dean of Trinity — was secretary to the delegates of the University Press, a man renowned for his taciturnity and an awesome remoteness. The youngest of his three daughters, Joanna Cannan, however became a writer of popular novels. With her children’s book of 1936, A Pony for Jean, she single-handedly introduced the “pony story” as a new genre in children’s fiction.

It was a long way from the works of Aristotle, beloved of her father, and it looks to be a waymark for the work of her three daughters who, between them, exploited the genre with an enthusiasm that was matched only by that of a worldwide readership of horse-obsessed girls.

Joanna Cannan had married Harold James Pullein- Thompson in 1918 and their daughter Josephine was born in 1924, followed a year later by the twins Christine and Diana (a son, Denis, the actor and playwright, preceded them in 1919). The three girls enjoyed a liberated childhood, educated — mornings only — at Wychwood School, Oxford, and, more rewardingly, all the year round in the country around their home at The Grove, near Henley — a period joyously recalled in their jointly written memoir Fair Girls and Grey Horses (1996).

What mattered most to them from the very beginning was working with animals, especially horses, and writing, and they combined these experiences first in a family magazine, typed by their mother, and then, during the 1940s, in a story which they composed together: It Began with Picotee.

“We used our father’s old typewriter which had no Rs,” said Josephine — and they would not let their mother near it for fear of being accused of trading on her reputation. Picotee was published in 1946, by which time the girls had established the Grove Riding School (which eventually ran to having 42 horses) and were also embarked on separate careers as pony-story writers. Christine’s first independent book was We Rode to the Sea (1948), which was quickly followed by what may still be seen as among her freshest and most engaging stories: We Hunted Hounds (1949), I Carried the Horn (1951) and Goodbye to Hounds (1952), titles which today’s publishers would blanch at issuing.

These books were the foundation of a writing life that spanned some 50 years and brought forth almost 100 books with translations into a dozen or so languages — a tally to which might be added well over 50 books by her sisters. Their popularity owed much to the affectionate and deeply knowledgeable treatment of the animal characters, beside whom the human participants often seemed rather rudimentary creations, and also to the brisk narratives which kept readers turning the pages, through many a threatened disaster, to the looked-for happy conclusion.

The stories were supplemented by several edited anthologies, such as Pony Parade (1978) and some excellent instructional books about riding, but in the 1960s Christine discovered a gift for writing tales about everyday life for younger readers, contributing family stories such as Granny Comes to Stay (1964) to the Reindeer and Gazelle series that were designed for children who had only recently learnt to read. She also moved into more general fiction for older readers, most notably with her two novels about the plight of a family separated by the Iron Curtain: Across the Frontier (1990) and The Long Search (1991).

The inspiration behind these stories may well have come from Christine’s husband, Julian Popescu, a radio monitor for the BBC who was half Romanian, whom she married in 1954. She moved with him and their family to Mellis in Suffolk during the 1970s where she eventually became chairman of the parish council and continued to be closely associated with country matters, especially through the Bridleways Group and through work for the disabled.

Only as the last century drew to a close did she give up writing, her last books — reverting happily to ponydom — being published by her daughter Charlotte’s Cavalier Press. She is survived by her husband and their two sons and two daughters.

Christine Pullein-Thompson, writer for children, was born on October 1, 1925. She died on December 2, 2005, aged 80.