Something you may have noticed about him is that his face is covered in a lot of his films. If there's a part where an intense character is wearing a muzzle of some sort, Hardy will take it. And he'll nail it, too.
Nolan explained why he decided to cover him up in Dunkirk. According to the director, "I was pretty thrilled with what he did in The Dark Knight Rises with two eyes and couple of eyebrows and a bit of forehead. So I thought, 'let’s see what he can do with no forehead, no real eyebrows, maybe one eye.'"
Nolan continued, "Of course Tom, being Tom, what he does with single eye acting is far beyond what anyone else can do with their whole body. That is just the unique talent of the man. He’s extraordinary."