Sherlock: The Six Thatchers (TV)

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...