甜食爱好者

The Missing Three-Quarter

Theory from Parts 1 and 2: The Blood Archive, and what Sherlock's connection to it (re: his blood sample) may be

Some sympathy for Godfrey's wife, and speculation on any continued role of his daughter

The Collector versus the Buyer: The two mystery players with Sherlock's blood sample

Closing Observations: The What and Why of those blood samples in The Missing Three Quarter

General Sherlock & Co Theory: Moriarty is the Principal's Brother, diving into ACD canon, and implications for the narrative of SH&C

Mariana’s age range (present-day)

States she’s Gen Z, not a millennial, in The Beryl Coronet (Part One)

Gen Z usually ranges from those born from 1997 to 2012

Now in 2026, that’s a range of people turning from 14-29 years old this year

Completed university education + already having had an overseas estate agent job 3 years ago + being included in the millennial talk by accident=>most generous range is 27-30 years old (born between 1996/1997 to 1999)

Most likely on the oldest end of that range, let’s say she’s 28 turning 29 years old this year. Would’ve been 25 years old when she met Sherlock and John

Lily’s age range (present-day)

Most likely substantially younger than Mariana, since Sherlock specifically points out her youth and mocks her as practically a child on the force ("Isn't it past your bedtime?" and "She’s young, her brain has been rotted by TikTok and memes and podcasts"-type comments)

Met Police website on DC eligibility and training states that you can apply to be a DC at 17, but you have to be 18 to start your training. Then there’s a 4-year  training period, at the end of which you earn the status.

18+4=22, that means that the absolute youngest Lily can be at present is 21 turning 22 sometime this year.

However, being more generous with that range and if she’s not freshly graduated from DC training, let’s widen the possible range a bit to include her possibly being up to currently 24 years old.

That gives us her turning anywhere from 22-25 this year, that leaves us with the tentative starting premise of Lily being born sometime from 2001-2004.

Lily’s age, continued (cross-referencing with how long Sherlock+Gwen have known each other, Lily’s age when Sherlock met her as a baby, and when Sherlock must’ve met Gwen Lestrade)

Sherlock describes when he met Lily for the first time, and Lily mentions that she was seven months old at the time

In CAM Part 3, Lestrade says that she's "known [Sherlock] for nearly 20 years". That episode aired on May 5th*, 2025, so if they didn't know each other for 20 years exactly, then the earliest they seemingly could've met (19 years before) is 2006

So, was Lily born either that year (2006) or towards the end of 2005 to account for being a seven-month-old when Sherlock met Gwen’s baby niece for the first time? (This is assuming that he had to have met Gwen at/before meeting Lily)

Nope. Neither 2006 or 2005 can be right for a birth year, because that doesn’t account for the 4-year DC training period, even if we count her application/acceptance year (2023 or 2024) as Year 1.

She would either be still a trainee and earning her DC status in 2027, or have just squeaked by and earned it crazy recently in 2026. With The Six Napoleons coming out this month (March 2026 at time of writing), there’s been nothing so far from Sherlock or Lily to indicate that she’s had the official job for barely three months, even though that’s easy math and it’d be natural for Sherlock to bring up her being young and only barely accredited.

However, if we interpret Lestrade’s comment slightly differently and say that she meant in CAM that they were coming up on some anniversary of her and Sherlock having met 20 years ago that year, but hadn't reached the specific month-or-what-have-you, then they could've met in 2005. Lily could've been seven months old when Sherlock met her and have been born in 2004.

If Lily was born 2004=>17 turning 18 in 2022, 4-year main training program, counting 2022 as Year 1=Graduated last year with DC status in 2025

She couldn’t have been born any earlier, because that would mean that Sherlock somehow met (and was trusted to hold) Gwen’s baby niece a year or more before meeting Gwen herself, without any reference to being pre-existing friends with Lily’s parent rather than Gwen. Meeting baby Lily slightly before Gwen would definitely smooth out the timeline a bit, but it just doesn’t seem likely. 2005 has to be when Sherlock and Gwen met, and thus Lily has to be a 2004 baby.

That would make Lily currently 21 years old, turning 22 later this year. If we take the CAM episode air date (May 5th, 2025) literally as very close to when that conversation happened, then Gwen and Sherlock must’ve met in May or June. With Lily being seven months, that means she must’ve been a fall/winter baby for the previous year. There are some issues with this regarding the DC starting point, but since she has her aunt leading the force, it’s possible to handwave it a smidge. More discussion of that here.

Sherlock’s age range (present-day)

Sherlock just had his birthday in January, and my sole starting assumption for his age range is that he can’t have just turned 40. I just wouldn't get it not being commented upon as ~entering a new decade~ by any of the trio (more on my reasoning in the bigger section here).

So, let’s set Sherlock’s upper age limit as just having turned 39 years old.

To get to the youngest he could possibly be right now, let’s consider that he must’ve started at Dulwich between 9-12 years old

Why that range specifically?

In Gloria Scott (Part One), Victor Trevor mentions that he and his parents moved to London when he was "around 9" years old. So, if he and Sherlock were in the same classes at Dulwich (which seems like the simplest explanation for Victor comparing their horrible grades)

Victor’s family came to England considerably well-off already, so it could've been that Victor started at Dulwich right away at that age as well. But that also likely means that Sherlock couldn't have started there before then, for the two of them to meet at the same time and to be peers (since there's no mention of any lonely pre-Victor year(s) at the school).

So, minimum possible age of Sherlock starting at Dulwich is probably 9 years old, maybe 10. If he got that 1999 letter from Mr. Musgrave the year that he started (since it’s logically the latest he could’ve possibly joined the school), then the youngest current age he could be now is 36-37 years old.

Sherlock can’t have turned 13 in 1999, because that would make him 40 years old now and break my first assumption. Also, going to note that there’s also a comment from Watson in a publicly available mailbag that clarifies Sherlock was there for boarding school, not in the more general definition of a UK “college” being for students in their late teens. More on that here.

So, working backwards, our broadest range has Sherlock logically somewhere between 36-39 years old (born between 1987 to 1990)

Sherlock’s age at Dulwich, and the age range for his expulsion

In Gloria Scott (Part Two), Sherlock mentions to Lionel Trevor that Victor “looked after me in a couple of turbulent years back in the school days"

With the most literal definition of “couple of", that would mean he was there for two years. Helpfully, Sherlock is a January baby, so even if he was kicked out before fully completing his second year in the spring/Lent term (per the Dulwich academic calendar), he would’ve almost definitely been the same age at expulsion as he turned that year. Even without a complete academic year, it'd make sense for him (or really anyone) to count passing two birthdays as spending a couple of years there.

However, you could argue that the language could also apply for if he was there for two full years and didn’t complete his third, so he’s rounding down. So, let’s say that he was there between 2-3 years, max.

I would personally lean towards the lower end of that range, taking Sherlock’s “couple of years” comment on its face, considering mentions from Victor and Reginald emphasizing how he wasn’t there long (more on this in the expanded section). All of those make more sense to me if Sherlock was kicked out sometime in his second calendar year at Dulwich (so either before the end of his second academic year, or early into the start of his third), spending two birthdays there, rather than settling into a third year.

So, with a starting age range of 9-12 years, then add three years for the absolute oldest he could’ve been=>Expelled at 12-15 years old. If we stick to just adding two years, then it’s a range of 11-14 years old.

However, we can narrow this down further. In Gloria Scott, after Sherlock’s “couple of turbulent years” comment, Lionel replies “Ha, the turbulent teens. I remember them well.”

Now, the rest of that conversation makes it clear that he didn’t actually recognize Sherlock out the gate, so he wasn’t thinking in relation to Sherlock being expelled. But, if he was working from the age when his son started, added two, and then came up with “oh yeah, that’s the range in which he would’ve known this guy”, concluding it was their teenage years, then that means that Victor must’ve reached 13 minimum if we go [The boys’ starting age at Dulwich]+[Minimum of two years there]=[Sherlock’s age at expulsion]

So, that shaves off the lower end of our age range for when Sherlock started at Dulwich, anything where adding two years results in <13 years old at expulsion age. So, since he can’t have been 13 to start with, we must have Sherlock, as well as Victor, starting at 11-12 years old there.

My inclination is for the boys to have started at 12 years old, since that puts Sherlock’s expulsion when he was 14-15 years old. So, with my +2 years assumption, he was most likely 14 years old when he was expelled. Considering the range for his birth year, that would make him 39 years old. If you consider him any younger, than you also have to push down the age when he was expelled in light of the 2-3 years he was there.

Years at Dulwich, and how old was Sherlock when he met Gwen and Lily Lestrade post-expulsion?

1999 also had to be his starting year for Dulwich, though it isn't stated as such in the episode. Expanded reasoning here with commentary on the Mr. Musgrave letter, but to summarize: if the youngest Sherlock could be now is 36 years, born in 1990, and the youngest he could’ve been starting Dulwich is 9, then the math doesn’t square with him spending 2-3 years there and being implied to be a teen when expelled.

So, add 2-3 years to 1999 for the latest he could’ve been expelled, and that gives us a range from 2001 to 2002. Since I’m favoring him being there for two years, in my mind, 2001 is the most likely of the pair.

So, I personally think he would’ve been at Dulwich from 1999 (12 years old) until he was expelled in 2001 (at 14 years old)

With that set, let’s jump forward to when he must’ve met Gwen (and Lily) Lestrade in 2005. Consider the date range for his expulsion, that’s a gap of 3-4 years between the two events. Backtracking to the full range of possible ages he could’ve been when he was expelled (from 9-12 at starting Dulwich, to expelled at 11-15 encompassing our “he was there 2-3 years” range), that means that he was between 14-19 years old when he met Lestrade. He must have been a teenager; he couldn’t have been turning twenty in 2005 (re:my self-imposed "he can't be 40 now" rule).

If we go with my preferred “started at Dulwich at 12, expelled at 14, currently 39 years old” chain, then Sherlock would’ve been 18 years old when he met Gwen, and not long after/around that time, was trusted enough to hold her baby niece.

It’s interesting to me that this would put Sherlock only slightly over the age of majority when he started his closest relationship in the force, compared to if he’d been a minor at the time.

I wonder if this was intentional, or at least has the potential to be explored. If he was more of a free agent hanging around the edges of the Met beforehand (i.e, possibly a runaway/kicked out after more failed schools/living with Mycroft, etc. but still seeking out detective work), maybe he put off directly approaching Gwen until he was a legal adult? That way his guardians/older-brother-who's-probably-not-keen-on-the-makeshift-criminology-career/social workers for minors wouldn’t have to be involved. More discussion of that in the expanded section here.