Written by Steven Moffat, ‘His Last Vow’ will air at 8.30pm on Sunday 12 January on BBC One and stars Lars Mikkelsen as Charles Augustus Magnussen.

Cumberbatch hinted at what viewers should expect: “…an incredibly steely reality which is harrowingly possible. [Charles Augustus Magnussen] is a businessman – he’s not a mad chaotic villain, not like the award-winning performance Andrew Scott gave as Moriarty. He is something of great calm and measure that has a depth to it which is an even bigger challenge than the chaos of Moriarty. He is so measured and precise – he is like a shark, a terrifyingly perfect predator of our age.”

The Star Trek Into Darkness actor added: “[Magnussen] will chime with people who know what a bully is – he is the archetypal bully and his means and methods are chillingly everyday in our culture. He’s a smart creation, very real and not fantastical. He’s got a foreign perspective on the English culture which Holmes so perfectly personifies and the fact that he fights on the side on the angels. He sort of reduces what Holmes protects.”

The official synopsis for the finale reads: “A case of stolen letters leads Sherlock Holmes into a long conflict with Charles Augustus Magnussen, the Napoleon of blackmail, and the one man he truly hates. But how do you tackle a foe who knows the personal weakness of every person of importance in the Western world?”

> Find out all the details on Series 3 in our news summary.

Are you looking forward to ‘His Last Vow’? Let us know below…

> Order Series 3 on DVD on Amazon.

> Buy the Series 1-2 boxset on Amazon.

Watch the Series 3 teaser trailer…