Asido, the Story of a Mexican Pony

Cecil G Trew was a pseudonym used by Mrs C Gwendolen Ehrenborg (1897–1959). She did much of her work for A & C Black, and is probably best known now as the illustrator for two of Primrose Cumming’s Silver Eagle books. She was as much at home drawing dogs as horses and people, and illustrated several dog books. She also wrote numerous instructional books on drawing. Out of the five children’s books she wrote, two were pony books.

Finding the books
Both books are easy to find, and generally reasonably priced.

Sources