Factual error: While this episode is set in 1946, early in the London street scenes a red Routemaster bus is prominently featured. The first of these buses was not delivered to London Transport until 1956.
Factual error: The episode takes place in 1946. Numerous scenes are shown in which the public buildings are clean. In 1946 they were soot streaked and grimy black and white from generations of coal fires and pollution. In addition one street scene has a street sign on a pole with a modern graphical notice on it rather than a worded notice of the time. Also, in the same scene the street name plate has a rather updated type face.
Factual error: A number of the cars have number plates in which the numbers precede the letters, whereas at the time the letters came first.
Factual error: Eternity Ring is set in 1946. Samantha was accused of spying because she was seen with a man outside The Old Vic. She admits seeing a play there but not the play alleged (Henry V instead of The Cherry Orchard). The Old Vic was bombed in the Blitz and was closed from 1941 to 1950.
Factual error: Foyle is disembarking from a trans-Atlantic voyage from a ship which, in long shot, is painted in Union-Castle line colours. This line served African ports, not the USA. Their ships had lavender-coloured hulls from the mid-50s.
Answer: They are using the accepted names of the bombs. During World War 2 the Germans used the metric system and produced bombs ranging from 50kg to 2500kg. Referring to the weight of the bombs in pounds (or fractions of tons) risked confusing the situation and would require someone to understand how to convert from imperial measures to metric, not an easy thing to do when under stress.