Eric Porter was only cast as Asher Smith after the actor first cast was injured in a riding accident.
Locations were found in Somerset while the pups were provided by the Heythrop Hunt in Oxfordshire.
James Hill read a review of the novel then read the book and used his own money to buy the film rights and tried to get Disney involved but it was too controversial for them. Once backing was secured the animal actors were raised exactly as in the book bringing up a litter of 8 hound puppies with a litter of 4 fox cubs from the day they were born. One of each paired off naturally so these two became Merlin and Tag but James soon found out that it was virtually impossible to train a fox as you would a dog and he wouldn't reveal how the shots of the hounds and the fox running together were done.
The impression of the violent accident near the end of the film was achieved by editing and without spilling any blood.
Thge tame fox used in the film was used to promote the film then spent the rest of it's life in a zoo.