WARNING: THERE ARE (QUITE MILD) SPOILERS AHEAD IF YOU'VE NOT SEEN THE BLIND BANKER YET!

It's perhaps a little inevitable that after the standard-setting opening episode of Sherlock last week, that the second instalment should not quite manage to match it. Yet, despite lacking just a bit of the wit and sparkle that was sprinkled throughout A Study In Pink, The Blind Banker nonetheless delivered another 90 minutes of genuine entertainment, the ilk of which we've not been used to getting on Sunday nights. And it's already got me looking forward to many more Sherlock adventures in the years ahead.

But for now, back to The Blind Banker. This was an adventure that arguably had just as tough a job as last week's opener. After all, writer Stephen Thompson had 90 minutes purely to dedicate to the narrative itself. There was no setting up of central characters and scenarios, instead an emphasis on telling one story, and telling it very well. Even Moriarty was left to, effectively, an epilogue at the end, taking up just a minute or two of The Blind Banker's running time. Fortunately, there was still plenty to get our teeth into.

The underlying story this time once more surrounded mysterious deaths, which Sherlock quickly pronounces as murders. The puzzle is that the victims are in rooms where there's no obvious way that the killer has got in. How could that have happened? Is Spider-man moonlighting? That's just what Sherlock and Watson intend to find out.

It's worth saying right here: the double act between the two leads here feels fleshed out and mature, and we're already only two stories in to this Sherlock's adventures. Whoever it was who ultimately threw Benedict Cumberbatch and Martin Freeman together deserves a very tasty drink, and can help themselves to a bag of Haribos too. It's already feasible to see these two working together for many years ahead (it feels, in a good way, as if they have been already) and I, for one, hope we get the opportunity to see that happen.

It's still a cold-ish working relationship that the characters have here, but The Blind Banker attempts to defrost Watson a little by focusing on him coming to terms with his post-army life. The most obvious manifestation of that is when he goes on a date, but predictably, that doesn't go quite to plan when Sherlock manages to gatecrash it. A thread has nonetheless been put in place that may be picked up on next week, as Watson very much remains a troubled man.

Sherlock himself meanwhile is still a relentless, chilly beast when he's in the midst of a murder case. Benedict Cumberbatch captures that terrifically well, and the desire for the writers to dig further into his character this early is tempered by the fact that he almost feels like the supporting act here. He's still the title character, but there's no desire to put him in as many scenes as possible, and if anything, it feels as if Thompson has chosen to pull back on deploying Sherlock too much, if anything. Watson is given his fair share of heavy lifting to do, instead.

Good on Stephen Thompson for this, too, because the mystery of the character of Sherlock is as compelling as the cases he's faced so far, for me.

This week's particular case involved ciphers, which appeared on walls and surfaces across London, and needed cracking. These ciphers, capturing the style of last week's instalment, consequently appear across the screen, too. That said, I didn't feel this effect worked quite as well this week as it did with the text messages and deductions in A Study In Pink. It's still a good device, though, with the symbols floating across the screen and, once again, it's not overplayed.

As Sherlock digs into the decoding of these ciphers, anyway, the mystery gradually unravels. Sherlock uncovers that it's a smuggling organisation that's behind them, using them to communicate. The key to decoding them? Ultimately, it's a book that everyone has.

Personally, I guessed this one incorrectly. I had it marked as a phone book, especially as we'd seen one earlier in the episode. And when it was revealed to be an A-Z, I wasn't utterly convinced that it is the book that each of us owns. But it still worked for the purposes of The Blind Banker, and for the second week running, I've really enjoyed following the clues to try and solve the mystery before Sherlock gets to it. The writing is good enough to let you play along.

I also liked the way in The Blind Banker that Watson was mistaken for Sherlock. I've seen things like this done in many contrived ways in the past, but here it worked well, and the layers were carefully put in place earlier in the episode.

Behind the camera, the difference between Paul McGuigan's superb, at times very still direction of A Study In Pink and Euros Lyn's handling of The Blind Banker was spottable. It's perhaps testament to the fact that these Sherlock adventures feel so cinematic that we're even talking about differing directorial styles with what's ultimately a TV series.

Lyn - who handled David Tennant's final Doctor Who story and Torchwood: Children Of Earth amongst many others - is a real talent, and he's happier to keep his camera moving here. I preferred McGuigan's slightly quieter approach (albeit with Bourne-esque action sequences), but Lyn has nonetheless done good work here. I'm first in line when he helms his debut big screen feature.

Credit again too to Stephen Thompson, whose script pushes Sherlock and Watson along as characters, while also putting together a decent whodunnit, and he's clearly had a lot of fun with the secret society that's at the heart of this particular story too.

Ultimately, though, I'm thankful for the quality of entertainment that this new Sherlock delivers once more. It feels fresh, interesting, exciting and utterly compelling at its best, and I'll be sad to see it leave our screens - for the time being, at least - this time next week.

It's been said by many already that Sherlock has been a major triumph for all concerned. The Blind Banker? It proves that A Study In Pink was no flash in the pan, even if it doesn't quite match it.

Read our review of Sherlock: A Study In Pink here.