Deliberate mistake: I don't think this film is supposed to be a biography, but merely a story which is based on actual events. In any case, when we first see Eric Lidell, it is 1920 and he has just returned from China to his homeland of Scotland. Eric would've been 18 years old in 1920. Ian Charleson, who was 31 at the time the film was made, looks his own age.
Deliberate mistake: OK so its arguable whether this is a mistake, since it was a deliberate attempt by the film makers to make the story more dramatic, but here goes: Eric Lidell didn't want to run on a Sunday, but that was the day of his race. The real Eric Lidell found out several months beforehand and had his event changed with virtually no fuss. In the film a chance remark by a journalist alerts Eric to the fact and he changes his event at the last minute. Are we supposed to believe that Eric, a world renowned athlete who has been training for years, would not know what events he was down for and what days they were on when he boards the boat to France? When was he planning to ask anyone? Would anyone have told him?