Joy Cowley (b.1936) was born in New Zealand. She is a phenomenally prolific author: she’s written over 400 books. She started off editing the children’s page for local paper the Manawatu Daily Times when she was sixteen, and went on to write stories for her own son. She had one printed in Short Story International which was seen by a publisher, and she was off. Amongst her books is one horsey trilogy about a Clydesdale horse. Bow Down Shadrach won the New Zealand Children's Book of the Year 1990. It may very well be that amongst her prodigious output are more horse stories: if you are able to help here, do please let me know,
Finding the books
Easy to find. The trilogy appears to be in print.
Sources and links
Joy Cowley’s website