In either the book or the movie or both, Fowles mentions as fact the statistic that in 19th century London, every third house was a brothel if I remember correctly (maybe every fourth house, and obviously not all in the same neighborhood). Statistics like these can be misleading even when they contain the truth or some morsel of it. I confess that I found it hard to believe when I saw/heard those numbers, but I guess it's not far from the truth :-)