There can be little doubting that the BBC’s modern-day adaption of the Sherlock Holmes stories is amongst the most popular dramas of today. Setting aside the soaps and the odd special episode of Doctor Who, the opening episode of the most recent miniseries, The Empty Hearse, achieved the highest consolidated rating for a TV drama in nearly a decade, with 12.72 million viewers tuning in. Steven Moffat and Mark Gatiss’s take on Sir Arthur Conan Doyle’s classic stories has clearly struck a chord with audiences, but it’s surprising to note the sheer scale of this success.

Considering the heights Sherlock was going to reach, it had something of an inauspicious start. There was no denying its pedigree; one of the co-creators had just shepherded a new incarnation of Doctor Who to the screen, and the other had a distinguished career in scriptwriting. However, the signs weren’t particularly good- Steven Moffat’s previous stab at the modernisation of a classic of Victorian literature, Jekyll, was received with critical praise but viewer apathy, and the production of Sherlock had been beset with issues, not least the need to rewrite and restage the pilot episode when the original running time of 60 minutes was deemed to be insufficient. With all of this considered, Sherlock’s immediate success was remarkable, with 9.23 million watching over the course of the week. Sherlock began big, and has simply got bigger and bigger- every series has outrated the last.

This wild popularity isn’t just confined to the UK, either; it has made international icons of the two lead actors. Both Benedict Cumberbatch and Martin Freeman were largely unknown outside of British acting circles- Freeman had gained some degree of notice as Tim in The Office but he was largely unknown beyond that, and Cumberbatch hadn’t received any notable degree of fame. However, both actors swiftly became leading Hollywood figures shortly after Sherlock aired. Freeman became the face of a multi-billion dollar franchise when he was cast as Bilbo Baggins in The Hobbit, and Cumberbatch has had his choice of roles, with him becoming the villainous Hollywood Brit de jour through his roles in Star Trek Into Darkness and the Hobbit, as well as roles in more challenging fare such as 12 Years A Slave, August: Osage County, and The Fifth Estate.

If the level of success that Sherlock has achieved is immediately obvious, the reasons why are perhaps less so. Perhaps the most obvious reason for its success is the fact that it’s actually a very good programme- intelligently written, well-acted all round, and with a willingness to assume that the audience is intelligent that’s rather uncommon in such a populist drama. The BBC have been savvy in its promotion and marketing, too- the first trailer for series 3 arrived nearly half a year before the first episode, unthinkably for a BBC production. Beyond all of that, though, is the fact that the modern show properly pays tribute to where it came from. Although decades of Holmes adaptations strewn with Victoriana may have convinced us otherwise, the originals weren’t period pieces- they had their finger on the pulse of contemporary society to a degree that matches extraordinarily well to the modern day. In the original Study In Scarlet, you read that Watson is a veteran of Afghanistan, struggling to find a roommate in expensive central London, and you wonder why on Earth it took so long for someone to realise how applicable it was to the modern day.

So, the question is- where next? The last series ended on a cliffhanger pointing to the return of the insane Moriarty, last having been seen blowing his brains out on top of a hospital. Attempting to guess where the series is going to go dramatically has, thus far, been fruitless (although the fact that Moriarty has a younger brother in the original stories may just be relevant to the character’s apparent return), but the real question is whether Sherlock can possibly maintain its ridiculous levels of popularity and acclaim. It remains to be seen, but it’s quite clear that the game is going to be on for the foreseeable future.