At the beginning of the movie, Roy asks his driver to let him off when they reach Waterloo Bridge so that he can walk across, and have the driver pick him up at the other end. The film proper is a flashback that takes place during his stroll. But in the final shot, when they should be driving away from the bridge, we see them starting to drive across it.
When Myra is talking with Roy at the Candlelight Club there is a reverse shot over Myra's shoulder of her right-hand fidgeting with her necklace. However, in the next immediate cut which is a mid shot of Myra, her right hand is now fidgeting with the ashtray.
When Myra and Kitty are looking out the window at Capt. Roy in the rain; the window from one cut to another cut goes from having a lot of visibility to having very little visibility.
The uniforms worn by the officers are more like US uniforms in cut and cloth than British. Roy's officer's hat is distinctly American in shape.
When Myra reads the list of 'Fallen Officers', there are names with the ranks of Sergeant (Sgt) and Gunner (Gnr). These are not Officer ranks.
When Roy travels back down to London from Scotland by express train, the train shown is a Great Western Railway one which did not serve Scotland as it only served routes from Paddington (London) to the West of England and Wales.
Robert Taylor speaks with a distinctly American accent although his family is clearly English. He made no attempt at an English accent. No explanation is given such as Cronin having spent time in the U.S e.g. schooling.
Even though the story takes place during the pre-1920 World War I period, all of Myra's clothes and hairstyles are strictly in the up-to-the-minute 1940 fashion.
When Roy and Myra are coming out of the Underground station after the air raid near the beginning of the film a traffic light is clearly visible in the top right hand corner. There were no traffic lights in London until 1931.