As of December of 2011 the BBC Archive states it has no information about "The Stallion," after repeated inquiries. It is a lost film, considered a lost masterpiece by some who saw it when it was first broadcast. One former BBC employee remembers seeing the film in the archive in the 1990s and believes it will eventually turn up.
The "stallion" used in filming was actually a gelding called "Nosey." When the filmmakers returned several months after the main filming to get a few additional shots of the horse they were dismayed to find it had grown a winter coat.