Alan C Jenkins was a prolific author, who wrote both fiction and non fiction for children. He wrote several titles for the Introducing... series, amongst which is Introducing Horses (1959). Amongst his fictional works is a story set in the Camargue, involving both iconic animals of the area: the bulls and the white horses.
Finding the book
The original British printing is tricky to find, though not impossibly expensive when it does turn up. The American printings are easy to find. Introducing Horses appears to be available as print-on-demand
Links and sources
The British Library
Bibliography: pony books only
White Horses and Black Bulls, Blackie, London, 1960, illus Victor Ambrus
Norton, New York, 1963, 112 pp, illus Victor Ambrus