In the title of Jonathan Smith's book "The Churchill Secret - KBO" on which this movie was based, "KBO" is an abbreviation for a phrase commonly used by Churchill; "Keep Buggering On" (in other words, don't give up).
As soon as she enters the bedroom intended for Sir Winston Churchill, Millie the nurse (Romola Garai), states there is insufficient space and that she will require access to both sides of the bed. The same thing was said by the nurse (Mary MacLeod) in Brideshead Revisited (1981), where the invalid is Lord Marchmain. Both dramas, made 35 years apart, were directed by Charles Sturridge. Coincidentally Sir Michael Gambon has also played Lord Marchmain, but in the later motion picture Brideshead Revisited (2008).
Sir Michael Gambon appeared in The King's Speech (2010), which also featured Churchill as a character. In Harry Potter and the Goblet of Fire (2005), he appeared with four other Churchills: Robert Hardy, Brendan Gleeson, Timothy Spall, and Gary Oldman.
The film takes place in 1953.