He conducted extensive research on the great detective and Sir Arthur Conan Doyle himself, and was very attentive to discrepancies between the scripts he had been given and Conan Doyle’s original stories.[37] One of Brett’s dearest possessions on the set was his 77-page “Baker Street File” on everything from Holmes’ mannerisms to his eating and drinking habits. Brett once explained that “some actors are becomers—they try to become their characters. When it works, the actor is like a sponge, squeezing himself dry to remove his own personality, then absorbing the character’s like a liquid”.[38]Brett was focused on bringing more passion to the role of Holmes. He introduced Holmes’s rather eccentric hand gestures and short violent laughter. He would hurl himself on the ground just to look for a footprint, “he would leap over the furniture or jump onto the parapet of a bridge with no regard for his personal safety.”[39]
It’s a great portrayal, but the later episodes when he was quite ill are hard to watch. He is still fantastic, but clearly struggling with his illness and the side effects of medication. Of course, by all accounts he smoked ferociously, but still.
It was definitely sad to see… On the other hand, Holmes was also a heavy smoker and, although he did quit cocaine in both the stories and the series (but at different points), he had abused his body for years. So that actually worked in-character as well.