How Holmes Solved the Yuletide Cipher
Dear Investigators,
This mystery was something of a sleigh-ride, but thankfully, your fine work has left us a step ahead of our enemies. Now that the The Yuletide Cipher is no longer a threat to Her Majesty’s safety, be sure to review Holmes’ own analysis, and how he identified the carol(ers) holding the key to this case.
Happy Holidays, and a Happy New Year to all!
The Dear Holmes Team
——
26 December, 1900
Dear Inspector Lestrade,
I trust this letter will find you well. I am pleased to inform you that, after careful analysis and collaboration with our American associates, I have finally lifted the fog enshrouding the Yuletide Cipher. Her Majesty is presently safe, and with your keen vigilance, and that of your colleagues, there is no doubt in my mind that she will remain so.
My estimation is that you will have deciphered some of the telegrams by the time you are holding this letter, but you may have a number of questions regarding O’Flaherty and his gang. I will thus explain what has transpired, and of greater significance, what might have befallen the Queen had the telegrams gone undetected.
Upon reviewing your first missives, dated 21 December, Watson himself noted that your case brought forth, not one conundrum, but rather a pair of singular mysteries – if not more.
Aldon O’Flaherty’s arrest alone was not deserving of particular attention, however, under the light of the enigmatic telegrams, and his own assertion of a threat against Her Majesty, he appeared to be party to a complex conspiracy. This I would soon be able to prove using evidence from your subsequent letters, though the questions would remain:
What were the telegrams concealing?
Who was sending them?
And if O’Flaherty’s tale was trustworthy at all, then how much of it, if any, was truth? How much of it was fantasy?
Unless your intercepted telegrams concerned the Queen, the evidence presented in your 21 December letters did not give any reason to believe O’Flaherty was connected to them. Furthermore, if the telegrams did concern the Queen, then that would have proven nothing beyond the fact that somebody was attempting to privately communicate about her (setting aside the possibility of a direct threat against Her Majesty).
Thus, I awaited new information before any additional scrutiny beyond that of the enciphered messages. Your preliminary analyses were excellent starting points, although you yourself quickly discovered the cipher was not a mere game of substitution; for the methods applied to the first one produced unexpectedly variable results when applied to the second one, or any of the later ones, we would learn.
I therefore decided to start by analysing the frequency of letters in the messages, as you did, but only after taking time to consider the significance of the telegrams’ other features: primarily, the consistent instances of “xx” and “zz”, and the notation of “time” placed beneath each telegram’s date.
Much like you, I speculated that the former were modes of punctuation or emphasis, meant to facilitate the interpretation of the messages (this was easy to verify once I understood the key to the cipher); but unlike you, I did not believe that “01.12” and “02.12” referred to the times at which the messages were written. If these were simple demarcations of time, then the two letters had been written exactly one hour apart from each other, on different days, which is both unecessary and highly unlikely. Barring the possibility of the messages being written at some symbolic intervals of time, I thought it was most probable that the “.12” numbers were substitutes for something unrelated to time.
Your second batch of letters arrived two days later, providing much of the information I would require to prove that theory and dispel this Holiday chaos. First and foremost, your account of Inspector Antonsley and Miss Bejard’s operation made it clear that Tadhg Doyle, who had delivered the telegrams to Trafalgar Square, was linked to O’Flaherty. The extent of O’Flaherty’s own involvement with the telegrams, and the connection (if any) between those telegrams and the previous toy robberies, was not plain to see, but if Doyle and O’Flaherty were part of the same gang, then our initial burglar was definitively connected to the Yuletide Cipher, as you had feared.
This news, we must not forget, also came coupled with another pair of telegrams. These were both dated 23 December, and beneath that, they had been marked like each of the others thus far. The fact that each of the intercepted telegrams had been marked with a unique number, followed by “.12”, was further confirmation to me that these numbers were irrelevant to time. My theory was that they had something to do with either the classification, or interpretation, of the messages. With regard to those messages, you were right to assume we were facing a form of substitution. Indeed your method of examining the frequency of letters, and trying to spot the letter “E”, might have produced successful results, had we been dealing with a simpler cipher. But as you rightly observed, a review of the most frequent characters in each message does not yield an obvious “E”. My notes, to follow below, confirm this.
Telegram “01.12”
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“T”, occurring 7 times. “E”, occurring 6 times.
“A”, occurring 5 times. “R” & “P”, both occurring 4 times each.
Telegram “02.12”
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“T”, occurring 8 times. “A”, occurring 7 times.
“S”, occurring 5 times. “E”, occurring 4 times.
Telegram 08.12
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“E”, occurring 12 times. “K”, occurring 6 times.
“I”, “M”, “S”, and “L”, each occurring 5 times. “T” occurring 4 times.
Telegram 03.12
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“E”, occurring 11 times. “T”, occurring 10 times.
“N” and “S”, each occurring 4 times. “U” occurring 3 times.
Telegram 05.12
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“E”, occurring 7 times. “I”, occurring 6 times.
“G”, occurring 5 times. “U” and “F”, each occurring 4 times.
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Considering the results above, you also speculated that multiple codes could have been at play. This we now know was spot on, Lestrade, but with only the information in your first 3 letters, I found myself at a standstill, fixated on the few crucial facts we had managed to ascertain:
that O’Flaherty claimed a plot was underway, involving “the Queen” – perhaps Her Majesty, perhaps a royally-named musical ensemble – and, that the burglars associated with O’Flaherty were also associated with the enigmatic telegrams, which, in light of their messengers, likely concerned criminal activity.
Thus, I requested information from you regarding the Queen’s itinerary, so as to make a crude, indirect attempt at deciphering the messages. I intended to analyse the telegrams alongside a list of notable sites (connected to REINA and, or, Her Majesty’s Holiday travels), and hopefully identify potential matches in the telegrams. From those matches I would then endeavour to work backwards towards a key.
To my surprise, I hardly had the opportunity to do so, for your brief explanation of Her Majesty’s movements also came bearing the unexpected gift of a solution. In your second letter of 23 December, you mentioned Her Majesty would soon be in Norfolk, where she would “remain until the twelve days of Christmas have passed”. When I first read those words, I was reminded of the contentious “hours” noted at the top of every telegram we had uncovered, and I thought to myself, “Another instance of 12.”
So I reviewed your earlier letters again, that time noting Constable Langley’s account of O’Flaherty’s bothersome “carolling”. Was our prisoner, I wondered, attempting to guide the investigation? If his carol of choice was “The Twelve Days of Christmas”, then perhaps he was. After all, a song with as many as 12 commonly known verses would allow for a simple yet deceptively varied mode of obfuscation. I verified this in my following attempts to decipher the telegrams, which were met with success; though had I been delayed, Langley’s further reports of O’Flaherty’s singing, presented in your letter of 25 December, would have confirmed my surmise and illuminated the key to the enciphered telegrams.
The telegrams, I should state plainly, indicate that O’Flaherty’s acquaintances have been closely following the Queen, Her Majesty’s, movements – they also suggest that an ambush was being planned for yesterday, the first day of Christmas. Needless to say, this attack failed to come to fruition. For that, you may thank my brother, Mycroft, whose discreet series of manoeuvres ensured that the Queen’s recent itinerary would be altered for the benefit of her safety, whilst a team of Mycroft’s colleagues, aided by several of my Irregulars posing as bricklayers, apprehended the scoundrels.
I expect your missing men – Taber, Martlet, and Mr. Scerbo – will have been sent back home from The Diogenes Club by now, in which case they will have been directed by Mycroft to inform you of the success above, and of the fact Darragh Kennedy is among those captured. I will further detail our results for you, but to truly understand the conspiracy against Her Majesty, and O’Flaherty’s self-sabotaged escape attempt, one must begin with the enciphered telegrams.
The simplest way of understanding what I have named the Yuletide Cipher is by regarding the number beneath each message’s date. This number – 01.12, 02.12, etc. – refers to which of the Twelve Days of Christmas, or rather, which of that carol’s verses, will serve as the telegram’s mode of encryption. Knowing this, one can merely write out the verse corresponding to the particular message’s number, and match each of that verse’s first 26 letters with those of the English alphabet.
For instance, 05.12 corresponds to the fifth day of Christmas, which according to the carol, refers to “Five golden rings, four calling birds, three french hen...” and so on and so forth. So the key to understanding this particular telegram is as such:
F-i-v-e g-o-l-d-e-n r-i-n-g-s,
A-B-C-D E-F-G-H-I-J K-L-M-N-O
F-o-u-r c-a-l-l-i-n-g b (i-r-d-s...)
P-Q-R-S T-U-V-W-X-Y Z
This allows for several different letters of the alphabet to be enciphered as the same letter (for example, “D” and “I” both become “E”), which in turn, complicates interpretation of the message for those without contextual knowledge. For the other telegrams, one would employ the corresponding verses as keys in the following way: “A partridge in a pear tree. A part...”, “Two turtle doves, and a partridg...”, “Three french hen, two turtle do...”, and finally “Eight maids a milking, seven swa...”
Bearing those phrases in mind, we can translate the five telegrams:
01.12
QUEEN RETURNED TO BUCKINGHAM. ADVISE.
02.12
NO. NEXT MOVE BOXING DAY. TO SANDRINGHAM.
08.12
MALL TO STRAND TO FLEET. THEN CANNON TO BISHOPSGATE TO LSS.
03.12
NEED TIME ANYWAYS. AO STILL OPPOSED. MAYBE OTHERS.
05.12
GIFTS RECEIVED. CARS LOADED. WILL REPORT BY BOX DAY.
Now, I urge you to consider the intelligence recently acquired from Mr. Doyle alongside this – my gratitude, again, to Antonsley and Bejard, for their valiant work. Based on Doyle’s statements about O’Flaherty’s past, and Kennedy’s “new chums” in America, we can piece together the events leading up to O’Flaherty’s arrest, as well as the events that ensued.
There is little doubt that O’Flaherty’s relationship with Kennedy soured as Kennedy acquainted himself, and later their gang, with Ronan O’Mally and his own American collaborators. The conflict between them then came to a boil when Kennedy began disseminating information about an upcoming violent plan aimed at Her Majesty. I surmise that O’Flaherty panicked as the “Important Dates” grew closer and took advantage of the burglary at Fawley’s to safely extract himself from the ordeal. His friends were likely correct in that he facilitated his own arrest, for in doing so, he had not only a way of thwarting Kennedy’s plot, but also a means of protection from the man, who was undoubtedly aware of his opposition. Kennedy likely had one of his men visit Bow Street in the days prior to the escape attempt, and once they determined where O'Flaherty was being held, Kennedy and company returned to “liberate” him and deliver their own variety of justice. This is the reason for which O’Flaherty, rather than fleeing, cried for help during the incident. Why he would not choose to cooperate more openly is difficult to glean, though I conjecture it has to do with honour more than reasoning in any case.
Mycroft will be paying a visit to Scotland Yard later this evening, at which point in time he will arrange for a transfer of prisoners. And once O’Flaherty knows that Kennedy has been apprehended, I am certain he will be inclined to sing a more useful song; the rest, I trust you can handle, especially with the likes of Antonsley, Bejard, and Langley by your side.
May the New Year meet us with more peace and tranquillity,
Yours sincerely,
