Deliberate mistake: Loch Ness is portrayed as a clear lake, as shown in the underwater scene. In real life, Loch Ness is so murky there is only six feet of visibility. Obviously deliberately done for the sake of the storyline.
Deliberate mistake: The taking of the famous "Surgeon's Photo" of the Loch Ness Monster from real life is worked into the fictional story of the film, which takes place during World War 2. The Surgeon's Photo was actually taken in 1934. Obviously deliberately done for the sake of the storyline.
Factual error: Loch Ness is an inland lake with very limited access into the open sea, or at least much less than portrayed in the film.
Answer: When Captain Hamilton and his troop first arrive he is greeted at the front door by Mrs. MacMorrow, Kirstie and Angus. He then says, "The housekeeper, Mrs. MacMorrow, is making all the arrangements," whereupon he realizes HQ failed to notify her of their arrival. Then Mrs. MacMorrow says, "When Lord Killin went off to the RAF, only a few of us stayed on here...I'm afraid I really would need Lord Killin's permission." Later it is also made clear that the shed (where Angus hangs out and Lewis Mowbray stays) was used by his father, who was a caretaker on Lord Killin's estate.
Super Grover ★