As the cast gathered for a first read-through of the only Sherlock episode to air next year, Producer Sue Vertue took to twitter to share a glimpse of the script.

This is what we’ve been doing today! Later on a pic of Sherlock and John as they’ll appear in the Special #221back pic.twitter.com/Aq4vncKpKy

— sue vertue (@suevertue) November 25, 2014

The one-off special will begin shooting next year with no firm details on a plot or transmission date, but we do know that a full fourth series (the standard 3x90min) will also shoot next year for broadcast on BBC One in 2016.

Sherlock returns in 2015 on BBC ONE.