Corrected entry: A quartz clock is shown (it being quartz can be understood by the movement of the second hand, jumping each second). It was only in the 1960s that the development of cheap semiconductor digital logic made their public and domestic use possible - their use before that was limited to some specific applications (like some scientific laboratories and so on).
Darkest Hour (2017)
1 corrected entry
Directed by: Joe Wright
Starring: Gary Oldman, Kristin Scott Thomas, Lily James, Ben Mendelsohn
Factual error: Neville Chamberlain is described as chairman of the Conservative Party. He was actually party leader. Party chairman is a separate post, which was held at that time by Sir Douglas Hacking.
Winston Churchill: My father was like God. Busy elsewhere.
Question: In the 'War Room' scene, there appeared to be a sheet of plastic or acetate covering the wall with the map of the enemy's movements. Was that premature for plastic to be available in that size for that time frame?
Correction: The second hand jumping each second is not unique to quartz clocks. An escapement providing a second hand that ticks once per second was invented in 1675 and popularised around 40 years later. It became the standard for pendulum clocks. So this clock is behaving perfectly normally for a mechanical clock.