Continuity mistake: When passing the lion in Trafalgar Square approx one hour in, the motorcycle sidecar swaps sides.
Continuity mistake: When Cyril holds the jar of Dad's jam he pulls off the lid along with the ribbon, but the ribbon is back on the jar in the following shots. (00:16:20)
Continuity mistake: When Miss Topsey and Miss Turvey first confront Phil, Topsey holds up the I.O.U. with her left hand, but in the next shot it's being held up with her right hand. (00:08:00)
Deliberate mistake: After the intro, the first shot of Isabel as she starts shouting about not fighting is a flipped shot. Note everything is backwards compared to the following shots. (00:01:15)
Continuity mistake: When Megs reads Norman's note in the barn about going to London, the message on the piece of paper starts off in portrait orientation and folded in half; then it becomes written in landscape orientation and folded into thirds; and then back again.
Continuity mistake: The side car is on the left of the bike. When they go past the lion the kids are on the right.
Suggested correction: This entry is for Nanny McPhee and the Big Bang (2010), not Nanny McPhee (2005).
Factual error: Farmer MacReadie tells Phil he knew of a pig that could play Scrabble. However Scrabble was not released until 1948, three years after the war ended.
Factual error: Albert Bridge is not found next to Battersea Power Station as depicted.
Factual error: When Nanny Mcphee is riding her motorbike and sidecar with the children towards Chelsea we see Battersea Power Station with four chimneys. Since the film was set in World War II, the station would only have had three chimneys - the B building being in the middle of being constructed.