Benedict Cumberbatch and Martin Freeman star as Sherlock and Watson respectively alongside Rupert Graves as Inspector Lestrade and Una Stubbs as Mrs Hudson.
The first episode of the new show will be called The Empty Hearse, a reference to the Sir Arthur Conan Doyle story The Adventure of the Empty House in which an apparently dead Holmes returned after several years hiding from his enemies.
Mark Gatiss has written the first episode, Stephen Thompson, who wrote the season two finale The Reichenbach Fall has written The Sign of Three and Gatiss’s series co-creator Steven Moffat has penned the final episode, His Last Vow.
The second episode will air on Sunday Sunday, 5 January with the third episode airing a week later.