Factual error: There is a scene where Chitty is pacing the train, which is an 'Austerity' tank engine. This engine was made during WW 2 but the movie takes place in the early 1900s.
Continuity mistake: In the candy-tasting scene with Lord Scrumptious, his head chef blows a whistle and holds it at chest level. In the next shot, Caractucus descends the stairs behind the chef, and now the whistle is down by the chef's side.
Continuity mistake: When Truly accompanies Mr. Potts and the children to the beach, her hair is first in a bun, and then later is worn down around her shoulders when they reach the beach. Also, the tightness or her curls vary from scene to scene while at the beach.
Answer: Dennis Waterman.