The Littlest Horse Thieves

Escape from the Dark is a movie starring Alastair Sim, Peter Barkworth, and Maurice Colbourne. When the owner of a Yorkshire coal-mine decides to mechanize to increase profits, the mine's pit ponies are scheduled to be destroyed....
When the owner of a Yorkshire coal-mine decides to mechanize to increase profits, the mine's pit ponies are scheduled to be destroyed. So, three children plan to steal them to keep them safe. But when they're caught, it's up to the mine owners and the miners themselves to decide what's right.