Written by Steven Moffat, ‘His Last Vow’ will air at 8.30pm on Sunday 12 January on BBC One.

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

Watch the trailer…

The official synopsis 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?”

> Order Series 3 on DVD on Amazon.

> Buy the Series 1-2 boxset on Amazon.

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