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.
Answer: Money.