Those non-Watson friends of Sherlock Holmes . . . they intrigue.
At the very start of Sherlock's career was Victor Trevor. And at the very end, we find so many: the private detective Barker, the on-a-first-name-basis-with-Watson Langdale Pike, and, of course, underworld agent Porky Shinwell Johnson.
"A very dangerous villain" with two convictions, called "Shinwell Johnson" by the fellows and "Porky Shinwell" by the ladies, Johnson wandered the dark corners of London where only familiar faces were welcome. As a man with "quick observation and an active brain," Shinwell was the right man for Sherlock Holmes to employ as an agent.
But looking at this dangerous criminal's two trips to Parkhurst on the Isle of Wight, one had to wonder about the length of his sentences and age of his first incarceration, to see how he would still be young enough in the early 1900s to serve such a purpose for Holmes. Parkhurst seems have been used as a youth prison, so that would help explain how he could be such a dangerous villain and yet not be locked away for too long a sentence. Which brings up another point . . . .
Did Sherlock Holmes first meet Shinwell Johnson when the felon was just a boy?
Could Shinwell have been one of the first Baker Street Irregulars, before taking a wrong turn in life? (And could that turn have been during one of Holmes's investigations, as Shinwell allied himself with some criminal for hopes at a higher reward than a shilling?) Trapped in prison for years after exposure to Sherlock Holmes might be the perfect incubator for an active mind to hone observational skills and the ability to move among the criminal element with ease.
Huge, as much from fat as otherwise, yet not so large he couldn't share a settee with Kitty Winter. Red-faced, and looking like he had scurvy . . . something scant few among us can even envision today, but Watson knew the look well. An illness surely from poor prison rations.
Yet he has resources once he's started to work with Sherlock Holmes, able to hide a woman in the suburbs, and he'll take instructions passed from Dr. Watson, who apparently knows where to find him. With Shinwell Johnson, we get a hint of the team Sherlock Holmes built around him in his latter years, perhaps taking a hint from Moriarty or the queen bee that an organization, even a small one, can accomplish much more than a lone man, even when he's Sherlock Holmes.
There is much to be learned from Shinwell Johnson. If only we had something more than "The Illustrious Client" account to learn from . . . .