A list of existing and former windmills whose sites fall within Greater London, England. When built, these mills were within the counties of Kent, Surrey, Middlesex, Hertfordshire or Essex. Of those windmills known to have existed, nine remain and are preserved; as are the tide mills at Three Mills, West Ham.
More than nine windmills remain preserved in Greater London, England.
The context mentions 9 windmills and others being preserved. maybe had trouble with the more than being not a concrete number?