Hartnell was brought up partly by a foster mother, and also spent many holidays in Devon with his mother's family of farmers, from whom he learned to ride horses. Reportedly, Hartnell had a fall and was kicked by a horse. An unspecified person applied disinfectant to the open wound in an apparent attempt to cleanse it. however, the disinfectant was of a type unsuitable for first aid purposes and caused blisters. The end result was a worse wound than would otherwise be the case. That left him with a large scar on his temple, which is actually visible in some of his stills shots even though it was covered with make-up during filming. He was a second cousin of the fashion designer Norman Hartnell.