Despite being cold enough for snow and icicles, no one's breath condenses while talking outdoors or in unheated train carriages.
In the flashback, set in 1863, the ruby is shown being locked in a safe. The safe has a single-dial rotary lock (a combination lock) which would not be invented until almost a decade later.
When the train arrives at the station, a young girl in a blue beret is seen walking with her family towards the exit. In the train window, there is a brief reflection of a DMU in B.R Green ( from the 1960's) class 108 . also, the locomotive pulling the train is displaying two different numbers.