I love the opening scene post-credits, with John doing battle with a self-service till while Sherlock does battle with a bloke with a scimitar! But how the heck did the guy get to the flat without drawing attention to himself?!

Cute moment: in the kitchen John sees the new scratch on the table caused (unknown to him) by the assassin’s sword. He tuts and rubs at it with his fingers while quietly muttering an exasperated “Holmes” under his breath.

It’s easier to see the interior of 221B in this episode because more of it takes place in daylight. Why is there a door onto the landing from the lounge and another one from the kitchen only a couple of feet away? It seems a strange layout and an unnecessary waste of wall space for such a small kitchen. The room layout was probably different in the past, but I’d have blocked up the kitchen door and put a cabinet over it. The tenants would also need a lot of keys to keep both doors locked while they’re out.

There also seems to be another door to the left of the fridge leading to a short passageway which has another door on the left a few feet along it. If that door goes to a room, it’s unbelievably narrow, ‘cause the stairs are only a couple of feet away. I suppose it might just be a very narrow bathroom.

As the boys go up the escalator at the bank, a wall clock shows the time in New York as 07:45. Later, when Sherlock starts dancing around outside Sir William’s office (great scene!), another clock says it’s 7:21 in New York.

I love John’s look of frustration when he takes the cheque from Sebastian and sees how much it’s for!

Sherlock takes photos of the symbols in Sir William’s office, then looks out the window at the nearby building (known as The Gherkin because of its distinctive shape). The top of The Gherkin is above the top of Sir William’s office window. He goes out onto the balcony and suddenly you can see over the top of The Gherkin. It’s clearly meant to be a Sherlock-eye view because the camera pans across slightly before looking down to the ground.

During Sherlock’s dance outside the office, there’s a column with a digital board on the left-hand side of the area. At one point he bumps into it and the whole column moves very noticeably.

I love Sherlock flirting his way into the flat of the woman living above Van Coon, although it’s a good job that Van Coon did leave his balcony door open or Sherlock would have been in trouble!

Why does Sherlock wait until the police have arrived before he starts to investigate Van Coon’s body and suitcase? I would have thought he would have started before they got there so that they wouldn’t interfere.

After all of Sherlock’s detailed explanation of how he knew that Van Coon was left-handed, a few minutes later we see Andy leaving a note at Soo Lin’s flat ... and he writes it left-handed. I was convinced that this was relevant, that I was very smart for having spotted it, and that left-handedness was going to turn out to be important throughout the episode, but it turned out to be just a coincidence that the actor was a southpaw!

Talking of left-handedness, Martin Freeman is left-handed but for some odd reason (perhaps a Martin thing rather than a John thing), he sometimes eats left-handed and sometimes right-handed. This may, however, have something to do with the fact that Martin had injured one of his wrists during filming.

Sherlock and John talk with Sebastian in the toilets of the restaurant. Sebastian gets a text from his Chairman saying that the police have said that Van Coon committed suicide. Sherlock says that they’re wrong and Sebastian contradicts him. Sherlock says sternly, “Seb,” but the subtitles both on the TV transmission and on the DVD say “So?” instead.

There’s a misprunt on John’s CV (apart from the fact that there’s no postcode after his address and he doesn’t give his full name): in the Employment History he lists (amongst other jobs) the “University Collgege Hospital”.

Adorable moment: Sherlock complaining that he asked John to pass him a pen an hour ago, not having noticed that he wasn’t even home. And I love the way John tosses him a pen without looking, and Sherlock catches it without looking. Benedict and Martin must have practised for hours to get it right (either that, or they mimed it and the pen was CGI’d in afterwards. I wish there was a commentary for this episode so that we could find out!).

Great line:
Sherlock: “This investigation might move a bit quicker if you were to take my word as gospel.”

Sherlock says that “the date stamped on the [library] book is the same day that [Lukis] died.” No it isn’t. Library books are stamped with the date on which they’re due to be returned, not the date they were checked out.

So, hang on: the killer follows Lukis to the library. While Lukis is looking for a book on one side of the aisle, the killer clears a shelf on the other side, without anyone noticing, sprays the code on the back of the shelf, without anyone hearing the hiss of the spray can, then moves out of sight. Lukis turns around, sees the message, realises he’s in terrible danger (possibly by finding an A-Z elsewhere in the library and translating the message), hurries to the exit, gets his book stamped, and runs for home. The killer saunters back into the aisle, puts the books back on the shelf, then chases off after him and arrives at Lukis’ flat long before Lukis does so that he has time to climb up onto the roof and get in through the skylight before Lukis gets through the door. OK, I think I’ve got all that clear ... um, wait ...

The only other way I can think of for the message to get onto the shelf is that the killer put it there before Lukis arrived. But even if he knew that Lukis would go to a particular section (which is, in itself, a bit of a stretch), he was a bit lucky that Lukis removed enough books from that one shelf to realise that there was a message behind them.

Anyway, why didn’t the killer, or Shan herself, just confront Lukis personally? It makes no sense for Van Coon and Lukis to be killed when the smugglers want to know where the jade pin is. There’s never any indication that they’ve been tortured before they were killed. And somehow I doubt that Van Coon would have held back the truth for very long if he had only been asked at gunpoint.

It’s obviously always difficult to film in a very public place like Trafalgar Square, and I’m sure they were on a limited budget and could only afford so many takes, but if I was a director there’s no way I would have allowed that shot of those two girl tourists so very obviously falling in behind Benedict and Martin as they’re walking along.

Great lines:
Sherlock: “I need to ask some advice.”
John: “What?! Sorry?!”
Sherlock: “You heard me perfectly. I’m not saying it again.”

John: “Me, Sherlock, in court, on Tuesday.” (In a rough accent) “They’re givin’ me an ASBO!”
Sherlock (absently): “Good, fine.”

I thought John was skint, but it doesn’t stop him jumping into a taxi to go to Scotland Yard rather than getting a bus or a Tube.

Real-life FYI: The actress playing Amanda, Van Coon’s PA who unwittingly had the jade hairpin all along, is Benedict’s long-time girlfriend ... and must therefore be killed to death very soon, please. ;-)

Sherlock goes through Van Coon’s receipts and finds a London Underground ticket bought at Piccadilly station. In real life there isn’t a Piccadilly station – the nearest name to that is Piccadilly Circus, but this is fiction so I’ll let it go. However, the ticket is mis-spelled “Picadilly” and that’s taking fiction a little too far. Also I’m not even sure whether Underground tickets state their purchase station any more. I would assume they’re more likely to give the zone they were bought in. And I’m a dedicated mad enough nitpicker to have seriously considered going down the nearest Tube station and buying a ticket just to find out, or accosting someone who’d just bought one to ask to have a look, but decided that I didn’t want to get arrested, or waste £4 on a theory!

Why does Sherlock take such an immediate interest in the apparently empty flat above the Lucky Cat? There’s absolutely no reason at all to believe – or even intuit – that there’s a connection, and Sherlock’s not the sort for gut feelings. And if – as we later find – Soo Lin had broken away from the smugglers, why the hell is she living above their shop?! The storyline in this episode is really quite bizarre at times.

I love John’s exasperation as once again he’s locked out while Sherlock’s investigating.

I also love the way that Sherlock’s eyes flicker from side to side when he’s rapidly thinking something through. It only happens occasionally but it’s very effective. It must be one of those things like rolling your tongue that some people can do and others can’t, and I’m one of the people who can’t (though I can roll my tongue!).

It’s broad daylight when John and Sherlock leave Soho. They go straight from there to the museum, but come out again in darkness, which seems a bit too long for them to have been inside. From there they go to the South Bank and start searching for evidence of more yellow paint. And (if the wall clock behind Sherlock at one point is accurate) it takes them until 11 p.m. to find it?!

If people (presumably Moriarty’s people rather than Shan’s) saw John find the wall of graffiti, they also must have seen him take the photo of the wall, so what was the point of painting over it before he got back with Sherlock? Was it just supposed to be a message warning Sherlock that he was being watched?

At the museum, Sherlock and John chase off after Soo Lin’s brother. She comes out of hiding, and her brother is immediately behind her and kills her moments later. So when and how did she manage to translate the first two words of the cipher, which Sarah finds later?

I love how Sherlock flirts with Molly, then drops his smile and looks impatiently at his watch the moment she turns away.

I’ve never been in the armed forces, but when Sherlock read out the translation “Nine mill,” I immediately thought of the 9 mm pistol (I have clearly been watching far too much Stargate ;-)). How come John doesn’t think of that possibility? Instead, he immediately asks if it means “millions.” Sherlock replies thoughtfully, “Nine million quid.” With his cut-glass accent, he doesn’t strike me as the sort of person who would refer to pounds as “quid.”

Every time I watch this, I get quite cross when Sherlock realises that the key to the cipher is the London A-Z. There are many editions and varying sizes of the A-Z – they even demonstrate this in the flashbacks which show that Van Coon’s and Lukis’ editions have different covers. And – nerd that I am – I turned my flat upside down to find my own copy and then followed Sherlock to page 15 ... which, as I already knew, is a map page, not the index. My index – and those in all editions that I’ve ever seen – is at the back of the book, and the page numbering follows straight on from the map page numbers. So unless the layout has been changed in recent years (my copy is at least ten years old) and unless everyone who would need to translate cipher was told exactly which edition to buy, the entire concept is impossible, and is very lazy writing. I don’t know if the idea of the cipher is taken from one of the Conan Doyle stories and has been given a modern twist but, if so, clearly the writer couldn’t think of a more sensible way of doing it and therefore came up with this nonsense.
And to make it even worse, even if the index is now at the front, there’s no way that Sherlock (or perhaps I should say Benedict) turns to page 15 in the close-up of him flicking through the book. I’d say he’s closer to pages 30 and 31 or so.

Why does the message on the railway wall say “Nine mill for jade pin”? It’s worth nine million; but this seems to imply that whoever brings it to Shan will be given nine million.

Why does nobody ever use the doorbells at 221? Instead, like others before, the Chinese guy knocks on the door instead of ringing the doorbell. Even if he didn’t know exactly which flat John and Sherlock live in, you’d think he would try the three doorbells.

I know that Sherlock gets absorbed in his work, but he’s standing only a few yards away from 221B when he looks through the tourist’s A-Z to translate the message ... and yet apparently doesn’t notice an unconscious John and Sarah being bundled out of the building. He’s even facing towards the flat the whole time!

Why do the kidnappers make the effort to look around the house and find Sarah but don’t find and take Mrs Hudson as well?

In A Study in Pink, Jeff said that Sherlock knows every street in London. Why, then, does Sherlock have to get a map out to look for the tramway? Plus he gets it wrong anyway: he stabs his finger down on the map at Covent Garden. Later, Shan says that the ‘show’ is coming from “the distant shores of NW1.” NW1 is much further north.

After pretending to shoot John, Shan reloads her pistol and says, “Not blank bullets now.” It wasn’t blank bullets before either, lady: that gun was empty.
[ETA: In an earlier draft of the script (released online later), Shan explained to John that her people had been deliberately firing blank bullets (at Sherlock) in the museum prior to Soo Lin’s death. This also explains why the gunman appeared to be a rubbish shot and didn’t manage to break the glass around any of the displays.]

Beautiful moment: John whispering an anguished “I’m sorry, I’m sorry” as the men carry Sarah’s chair over to the crossbow.

After reloading her pistol, Shan cocks it. Sherlock then arrives at the end of the tunnel and she turns and aims her pistol towards him ... and cocks it again.

Great lines:
Sherlock: “How would you describe me, John? Resourceful? Dynamic? Enigmatic?”
John (tetchily): “Late?”

Sherlock, you blithering idiot, there are bad people in the tunnel who are not going to stand around meekly while you try to untie Sarah. So tip the bloody chair over and get her out of the line of fire! I’ll forgive Sarah for not thinking of trying to do it herself, but super-smart Holmes has no excuse for leaving her in mortal peril like that.

Sweet moment: Mr. Emotionless putting a comforting hand on Sarah’s shoulder after he has untied her.

This was the weakest of the three episodes. There are plot inconsistencies you could drive a London bendy bus through, and it doesn’t have the same atmosphere as the first (or third) episode. Some of this may be because the director of this episode (Euros Lyn, well-known for Doctor Who) didn’t use as many close-ups as the director of the other two episodes, and this distanced the audience from the action.

I also think that Steven Moffat and Mark Gatiss didn’t spend enough time with the writer of this episode, Stephen Thompson, to ensure that he knew exactly how the characters should interact. Sherlock was much too aloof and superior in this episode and didn’t have the same relationship with John as he had had in episode 1. And if you look at how many Great Lines I quoted from episode 1, there are, what, just four for this one?

It’s also a shame that Lestrade wasn’t in this episode. Presumably Rupert Graves wasn’t available, and I know that Lestrade wasn’t in all the original stories, but it’s a pity that such a well-established character from Conan Doyle canon wasn’t around in only the second episode.

We cut back to the supermarket just as John enters the last two digits of his PIN into the card reader. As he presses the two keys (which appear to be 7 and 4) they beep two different notes. That’s not how those little card readers work – they don’t play a tune so that anyone nearby can work out your number! Also, it doesn’t look like John presses the Enter key with his right thumb – he seems to push a button higher up. No wonder the machine wouldn’t authorise his transaction!

I think I’ve come up with a reason why Lukis’ library book is stamped with the same date that he died. (I don’t usually try to explain away plot inconsistencies, but I’m fond of the Executive Producers ;-)) Maybe the book was due back that day and that’s why he went to the library that night. Now, I must admit I’ve not been to a library for years, but isn’t it normal to hand in the books you’re returning as soon as you arrive, and then go and get new ones? But at least it would explain why he’s carrying a book with that date on it – he didn’t hand it in on arrival, then saw the spray-painted message (and I still don’t understand how it got there), translated it and then immediately fled in terror without thinking to give the book back.

John arrives back at 221B after his arrest. The first Sherlock knows of it is the sound of a door slamming. Without turning round from the mantlepiece, he says, “You’ve been a while,” and behind him, John walks through the open door of the living room. So which door slammed? It wasn’t the downstairs front door, because John didn’t have time to get up the stairs. Did he slam the kitchen door as he passed by, just to signal his (annoyed) arrival? I guess it’s possible, but it would have helped if we’d seen him do it.

There’s also a sort-of explanation of Sherlock’s interest in Soo Lin’s flat. I hadn’t noticed before but while sitting in the restaurant opposite, he spots the Yellow Pages on the doorsteps, presumably also realises that it’s wet and so has been there for several days, then he glances upwards – and it’s presumably then that he sees that her windows are open. Until now I thought he didn’t see open windows until he went round to the back of the building. However, it still doesn’t explain why he would care about this empty flat.

On the subject of the cipher painted on the wall by the railway track, if it’s that relatively easy for the public to get onto the track (and there’s no indication that John and Sherlock have any difficulty), there’s no way that the cipher wouldn’t have been joined by all sorts of tags from other random graffiti sprayers – not unless someone’s guarding the wall 24/7 and chasing them away. Which I suppose is just about possible, but it’s a bit of a stretch.

Who IS the “Opera Singer” listed in the end credits? Am I having a complete moment of idiocy or does she not appear in this episode at all?

So I finally found out who the “Opera Singer” in the final credits is – it’s General Shan! According to someone on another forum, Chinese acrobatic troupes are often known as opera companies. While the title might be factually accurate, I still don’t understand why they couldn’t have just credited her as “General Shan.”

Why did I not notice the most supreme piece of acting in the whole series until someone else pointed it out on another forum? Shortly after the boys first sit down with Sebastian at the bank, he tells John that everyone at university hated Sherlock. The camera switches to Sherlock, and if Benedict Cumberbatch ever deserved a BAFTA, it’s for the way that Sherlock turns his head and tries to hide the look of pain and distress that crosses his face.

My previously expressed opinions about the scenario in the library are utterly vindicated in The Partially Sighted Postman, a totally hilarious spoof of the episode. I almost had a heart attack, I was laughing so loudly (and applauding) during the library scene!

Just to clarify: 185 North Gower Street is the address of the location they used to film the exterior of 221B Baker Street.

Warning: you do need to have also seen The Great Game to get all the jokes, plus a lot of the jokes are rather British. But you should read it anyway for the library bit!

Some time ago Benedict confirmed that the moment when John tosses a pen (without looking) to Sherlock who catches it (without looking) was genuine and not CGId. He said in an interview that he actually caught the pen first time but they had to re-shoot it about four times before the director was happy.