If you think that's impressive, Jeremy Brett did that on his own!

Brett was approached in February 1982 by Granada Television to play Holmes. The idea was to make a totally authentic and faithful adaptation of the character's best cases. Eventually Brett accepted the role; he wanted to be the best Sherlock Holmes the world had ever seen.[37] 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.[38] 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".[39] 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."[40]

https://en.wikipedia.org/wiki/Jeremy_Brett#Sherlock_Holmes