Looking back over the list of actors who have played Holmes, it’s surprising to what degree performances stand or fall by the actor’s capacity to acknowledge this shadow self. An example of how not to do it came with Elementary, the other contemporary Sherlock drama that features Jonny Lee Miller as Holmes fresh out of drug rehab and living with Lucy Liu’s Dr Watson. The writers of Elementary pay lip service to the alien side of Holmes, but Miller offers a performance devoid of human warmth, all gleaming teeth and swivel-eyed self-interest. In Guy Ritchie’s two recent films, meanwhile, Robert Downey Jr turns in a smirking action-hero genius in a leather waistcoat to go with Iron Man’s smirking action-hero genius in a metal suit, but the Hollywood hyper-confidence of his performance strips out nearly all nuance from the role.