As Max and Dodds talk in Parade Gardens, with Pultney Bridge in the background, a group of seagulls flying over the river disappear between shots.
When Max and Dodds are talking in the garden at Max's party, Max grabs Dodds by the arm. In the next reverse shot Max is not holding his arm.
The Colt 1911 has never been used by the British Military.
For the friend who wrote that Byzantium was not a town. Actually it was. before Instabul or Constantinopole, before the East Roman empire, Byzantium was the name of the town-colony Greeks made in 658 BC. Their king was Byzas, and he gave his name to the new city.
During her chat with DCI McDonald, Mrs Wattel refers to Bath as a city-state, like Renaissance Florence or Byzantium. Florence was indeed a city-state, but Byzantium was not a city at all. It was the eastern half of the Roman Empire for a millennium and controlled modern day Turkey, Syria, Lebanon, Israel, much of Greece, Bulgaria and Egypt. Its capital was Constantinople, now known as Istanbul.
The phone number on the sign outside the refuge is 01632 960552 (matching DS Dodds' notebook entry). But a Bath phone number should have an area code of 01225. 01632 is reserved for use for purposes such as this fiction.
When McDonald and Dodds discover the USB drive at the allotment, McDonald proceeds to immediately plug it in to her computer to see what it contains. This would be completely contrary to any accepted police digital forensic procedure which McDonald would have had at least sufficient training to know.
In the frame at 00:52:30, when a photographer is taking a group photo at Max's party, they covered the brand name of the camera and that of the lens but the model of the Canon camera EOS is clearly legible.