"He was once Senator" [THOR]
My high school Latin teacher was a great admirer of Julius Caesar, and I suspect secretly felt that she, who ruled the classroom with an iron hand, might have managed the Roman republic and empire better than Caesar himself had done. Certainly she might have avoided the assassination at the hands of a political cabal that famously took place on the steps of Rome's senate-house on March 15 in the year 44 BC — the Ides of March.
Tomorrow is the Ides, and a few admirers of Julius Caesar may be wearing black in his memory, though not the "complete mourning" that was customary for the bereaved in the 1890s (as mentioned in "The Greek Interpreter"). The Ides are a crucial part of the Roman calendar, which numbered days not from the beginning of the month but in a countdown like the reckoning of shopping days left before Christmas. The crucial days were the mid-month Ides, the Nones about a week before, and the Kalends at the beginning of the next month.
Today would be recorded as "ante diem i Idibus Martius", the day before the Ides. Sherlock Holmes probably knew that; he could read Latin — he quotes it once or twice, and bought a book in Latin, as noted in A Study in Scarlet. He describes it: "De Jure inter Gentes — published in Latin at Liege in the Lowlands, in 1642. Charles's head was still firm on his shoulders when this little brown-backed volume was struck off." Struck off, like the head of King Charles I, executed for treason in 1649, the victim, like Caesar, of a conspiracy or a popular uprising, whichever you choose to consider it.
It is easy to forget nowadays that Caesar was a dictator, a tyrant, possibly a proto-fascist; that's why Brutus and the other assassins decided he had to go. One of my classics professors in university remarked tellingly that "No one really understood Caesar until Hitler came along." He has, though, been compared to Napoleon — whom Sherlock Holmes also knew well. Interestingly, too, my textbook edition of Caesar's autobiography, the Gallic Wars, had footnotes comparing his military strategy in northwest Europe with the lines of the trenches in Belgium during World War I, 1,900 years later, terrain familiar to Arthur Conan Doyle.
Julius Caesar is not mentioned in the Sherlock Holmes stories. There are a couple of characters named for his adopted son, Augustus, but that's the closest it comes. (No Brutuses (Bruti?), either.) Holmes and other figures often refer to "assassins," but generally use the word as a synonym for murderers. Possible political assassinations that do get a mention are "the Trepoff murder"[SCAN] and the work of "Huret, the boulevard assassin" [GOLD]. Sherlock Holmes says in A Study in Scarlet: "Political assassins are only too glad to do their work and to fly. This murder had, on the contrary, been done most deliberately."
Best of all is this passage in "The Bruce-Partington Plans": "It is well they don't have days of fog in the Latin countries — the countries of assassination. By Jove! here comes something at last to break our dead monotony." There could hardly be a more Latin country than Rome, and Holmes drives the point home when he swears by Jove, or Jupiter, the Roman king of the gods.
One other note about the Ides of March: one of the ugliest murders in the Canon takes place on that date, March 15, in (probably) 1897. It is the precipitating event of "The Devil's Foot." And it is set, oddly but indisputably, on the day when Arthur Conan Doyle met, and apparently instantly fell in love with, his second wife, Jean Leckie.