In the episode A Scandal in Belgravia (S02E01) there is a very kinky reference in which a princess (Lucy Page) is tied to a bed while Lara Pulver walks in the room with a flogger and asks her if she has been wicked...
Clip: https://sendvid.com/c8wdb1uo
IMDB: https://www.imdb.com/title/tt1942612/