One More Pony
A&C Black, London, 1952, illus Mary Shillabeer

Pony Trek
A&C Black, London, 1947,  illus Mary Shillabeer

Pony Boy
Lutterworth, London,1958

Hilda Boden wrote many children’s books as well as her pony titles.  Her Joanna books are a pair, about a a girl whose guardians who are supposed to be looking after her, and her farm, but have to say the least of it, evil designs.  The second book sees Joanna in much happier circumstances.  Hilda Boden wrote no other pony series, though her children’s Marlow Family series reached several titles.  

Her Crown Pony Library titles are the easiest to find:  Pony Girl  in particular.  Pony Trek is very hard to find with its dustjacket, and probably the hardest overall to source.  Joanna Rides the Hills can be tricky. All the other titles are reasonably easy to find.