"Delighted to have Toby Jones on board, bringing to life one of Doyle's finest villains."

So said Steven Moffat this week, casually pouring gasoline onto the flames of Sherlock series four speculation. Of course, Moffat and his co-showrunner Mark Gatiss are nothing if not gleeful liars, and we wouldn't be surprised if this ends up to be a red herring to disguise the fact that Jones is actually playing a non-villain - maybe that third Holmes brother we've been speculating about for years now.

But let's take Moffat at his word for now, and assume Jones really is playing a wrong'un. Here's a rundown of six of Doyle's finest villains, beyond Moriarty and Magnussen, to fuel your predictions.

1. Sebastian Moran

In truth, we'll be pretty disappointed if Jones turns out to be playing anybody other than Colonel Sebastian Moran, Moriarty's right-hand man. Moran did make a blink-and-you'll-miss-it appearance in series three's 'The Empty Hearse', but as we said at the time, it's pretty hard to believe Moffat and Gatiss would just let one of Doyle's most memorable villains, "the second most dangerous man in London", go to waste.

Moran is essentially the Watson to Moriarty's Holmes - an accomplished ex-army colonel whose loyalty knows no bounds - and in the original story, he reacts to Moriarty's death by pursuing Sherlock to London and trying to kill him once and for all. In the Sherlock canon, maybe his retaliation begins by masterminding Moriarty's "Did you miss me?" appearance on TV screens across the nation.

One big problem with this theory is that Jones is appearing in episode two of the new series, not episode one. Given the way 'The Abominable Bride' ended, it's pretty clear series four will be kicking off immediately with the next stage of Moriarty's plan, so saving Moran for episode two seems unlikely - unless he's going to be gradually teased and introduced late in the game, like Moriarty was in the first series.

2. Henry Peters

The Disappearance of Lady Frances Carfax is probably the story we're most eager to see Sherlock tackle in series four, especially with all the promises we've been given about "darkness" and "consequences".

It's one of Doyle's more downbeat and unsettling stories, and Australian conman Peters is a memorably unsettling villain - he tricks Lady Carfax into going away with him by posing as a philanthropic man of God, and buries her alive in a coffin so cunningly designed that Holmes and Watson almost fail to save her. It's unusual for any bad guy to truly outsmart Holmes, even briefly, so Peters might just qualify for classic villain status.

3. Brigham Young

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If that name sounds familiar, it's because Young was a real person - he was one of the first leaders of the Mormon Church. He's also, chronologically, the very first Sherlock Holmes villain. Doyle's first Holmes novel A Study in Scarlet was actually banned from some US reading lists for being anti-Mormon, and however you feel about censorship it's pretty tough to argue with the interpretation.

Along with the joyous first meeting of Holmes and Watson, the book spends huge chunks of time flashing back to 1847 Utah, where a young pioneer girl named Lucy is saved from death by a group of Mormons. She and her father convert to Mormonism, and years later... Well, let's just say it doesn't end well. The whole church comes off pretty badly, but Young himself is probably the most active villain of the piece, along with a pair of Mormon thugs named Stangerson and Drebber.

Since the whole Utah plot was completely excised from Sherlock's 'A Study in Pink', it's still a storyline ripe for the taking, if a bit impractical for modern-day London. Book of Mormon is still running in the West End, right..?

4. Dr Grimesby Roylott

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Roylott is the villain from The Adventure of the Speckled Band, aka The One With The Snake. A classic locked-room mystery, the story centres on a young woman who comes to Holmes because she believes her life is in danger, following the mysterious death of her sister.

Her wealthy but aggressive stepfather, Roylott, is the prime suspect, but what's really memorable about this guy is his weapon of choice.

5. John Clay

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One of the Sherlock Holmes stories' most brilliantly weird mini-plots was The Red-Headed League, a club open only to men with red hair of a very particular "flame-like" hue. This unlikely secret society was all a ruse, invented by career criminal John Clay as part of his grand plan to dig a tunnel into a major London bank. You couldn't make it up, but Arthur Conan Doyle could.

OK, so The Red-Headed League isn't the most likely choice for Sherlock's next adaptation - it barely has enough plot to sustain a short story, let alone a 90-minute episode - but Mark Gatiss has hinted at it before.

6. Jonas Oldacre

Now that we know (ish) that Moriarty is dead after all, maybe it's time to introduce the one villain in Holmes canon who actually did fake his own death - a crafty builder by the name of Jonas Oldacre.

The Adventure of the Norwood Builder isn't a particularly memorable story, except for the fact that it takes place just after Holmes has returned from the grave in 'The Empty House', and features a villain doing the same. Oldacre wanted revenge on his former fiancée, who'd dumped him years earlier after realising he was the worst, and planned to get even by framing her son for his murder. Sort of proving her point, there.

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