Steven Knight highlighted a moment during series 2 when Tommy Shelby obtains medication, and somebody says, “That’s for horses.” In response, Tommy Shelby says, “I am a horse.” Knight found this to be a perfect example of why the horse motif is so important to the show.
“In a way, he is [a horse],” Knight said. “It’s about him wanting to escape in the way of the horse, not having the intricacies of being human but running out there, that’s what he wants.” The showrunner also said that it’s common for people who own horses or are often around them to have dreams where they become horses, which is something he wanted to imbue in Tommy:
“Good and bad, right and wrong seem to be blurred in Tommy’s world because he blurred them himself. He does bad things, he does wrong things. But there’s the black horse and the white horse. In other words, ultimately there is good and bad, there is right and wrong, there is life and death. They represent the idea that somewhere there is some certainty. For Tommy, that’s as close as it gets to religion.
It’s hard not to immediately think of Peter Shaffer’s “Equus,” the brilliant stage play about a young man who has a pathological, religious fascination with horses. Of course, Tommy Shelby’s connection to horses is nowhere near as harrowing as the one portrayed in “Equus,” but the existence of the play emphasizes Knight’s point: horses make for strong, symbolic storytelling.