Series 4 of Sherlock will open with “The Six Thatchers”, premiering 1 January 2017 at 8.30pm to 10pm on BBC One.

Synopsis:

In episode one of this new series, written by Mark Gatiss, Sherlock waits to see where Moriarty will make his posthumous move.

One mysterious case in particular baffles Scotland Yard – but Sherlock is more interested in a seemingly-trivial detail. Why is someone destroying images of the late Prime Minister Margaret Thatcher? Is there a madman on the loose? Or is there a much darker purpose at work? Something with its roots deep in Mary Watson’s past…

Benedict Cumberbatch returns as Sherlock Holmes, with Martin Freeman as John Watson, Mark Gatiss as Mycroft, Rupert Graves as Inspector Lestrade, Una Stubbs as Mrs Hudson, Amanda Abbington as Mary Watson and Louise Brealey as Molly Hooper.