Dennis Peck lived in the Cotswolds, and farmed there until he gave up farming to write and compose music.  He hunted with the Heythrop on the real life Bess, his favourite horse.  Bess’s story was written for his youngest son.  

Finding the book:  reasonably easy to find.

Sources and links:

Dustjacket of Bess

Dennis Peck

Bess, the Story of a Horse

George Ronald, London, 1960, illus Marjorie-Ann Watts, 143 pp.

Old Bess, out to grass, and in charge of two very young thoroughbreds colts, tells them the story of her
life and how she ran in the Grand National.

Bibliography - pony books only