1. Holmes and Watson are good enough to eat
Speedy's Cafe, the sandwich emporium frequented by Holmes and Watson in the series, is a real café on Gower Street, near Euston - the BBC's stand-in for 221b Baker Street. The fans who flock there from all over the world can now enjoy specially created Sherlock-themed snacks, specifically the Sherlock wrap or the Watson Wrap.
2. Despite China's best efforts, Sherlock isn't gay
As amply demonstrated by the kisses in season three's first episode, The Empty Hearse, Steven Moffat and Mark Gatiss have always enjoyed flirting with the ambiguity of Sherlock's sexuality. "Everyone recruited him to their perspective, their interpretation," Benedict Cumberbatch once said when asked about Holmes's sex life. "I've had asexuals come up to me and thank me for representing asexuals." But they're mistaken, according to Moffat: "There's no indication in the original stories that Holmes was asexual or gay," he told The Guardian. None of which has stopped millions of Chinese fans from adopting Sherlock as a gay icon, with a vast archive of literature dedicated to his romantic exploits with Watson.
3. His pen-catching skills are beyond reproach
A scene in The Blind Banker shows John throwing a pen to Sherlock, who catches it without even looking at it. Cumberbatch made the catch on the first take (using a mirror so he could see it coming), but the cameraman was too slow and missed it. He got it again on the third.
4. '221b Baker Street' actually looks like this
The 370 sq ft one-bedroom flat above Speedy's Cafe, which is in fact about a mile away from Baker Street but doubles as Sherlock's home for exterior shots, was available for rent in early 2012 for the price of £330 a week.
5. Sherlock's staircase would please purists
In Conan Doyle's A Scandal in Bohemia, Sherlock asks Watson how many steps lead up to their quarters at 221b Baker Street. Watson hasn't a clue. "I know there are 17 steps, because I have both seen and observed," Holmes tells him. Because Sherlock fans are similarly observant, there are 17 steps leading to the first floor of the Sherlock Holmes Museum, and another 17 between the hall and front room on the Cardiff set of Sherlock.
6. Matt Smith wanted to be Watson
A week before landing the part of Doctor Who, Matt Smith auditioned to play John Watson; Steven Moffat decided he was "too barmy", and that one Sherlock was enough. Martin Freeman, on the other hand, arrived at his audition having had his wallet stolen on the way and was in such a bad mood it was assumed he wasn't interested. The following week, he returned in a better frame of mind, read with Benedict Cumberbatch, and the part was his.
7. Benedict Cumberbatch hates Sherlock's hair
The actor's preparations for looking the part of Sherlock include intense Bikram yoga sessions, swimming, and no smoking or drinking during filming. But there's one thing he especially hates doing: growing his hair. As he told The Times, "I can't think of a wittier or even accurate comparison, but I just think it makes me look a bit like… a woman."
8. But he may be autistic
Late 2013, autism charity the National Autistic Society cited Sherlock's single-mindedness, inability to understand social norms such as sarcasm, and incredible feats of recall as evidence that he might be autistic. This, despite Watson making a direct reference to his friend's Asperger's in The Hounds of Baskerville.
9. Mark Gatiss learnt to swim in Moriarty's pool
At the end of season one, Moriarty lures Holmes and Watson to a beautiful public pool in order to kill them. The location used is Bristol South Swimming Pool; according to the Sherlockology blog, this is also where a young Mark Gatiss learnt to swim.
10. Sherlock and Mrs Hudson knew each other in a previous life
Benedict Cumberbatch has often said that Una Stubbs (above), who plays his screen landlady Mrs Hudson, mothers him on the set of Sherlock. But she has good reason: Stubbs is an acting contemporary of Cumberbatch's mother Wanda Ventham, and used to live around the corner from her when Cumberbatch was a child.