In the final shots, a large British flag attached to a mews gate is in fact the Flag of Great Britain, which lacks the diagonal red cross of Ireland, the St. Patrick's Saltire. In 1958 it's more likely that the set dressers unknowingly picked the pre-1800 period flag from the movie studio prop store than that people in 1945 found such a flag when correct Union flags would have been far more available to celebrate the end of the War with.