The following is the population of the historic county of Middlesex (including the City of London) as given at each ten-yearly census from 1801 to 1881:
* The figures for 1881 in the source do not cross-cast precisely. The source gives figures for a very large number of subdivisions of the hundreds etc, including parishes and many small extra-parochial areas, especially in and around the City of London. The treatments from one census to the next are not precisely consistent.
References
Population of Middlesex (1801–81) Wikipedia(Text) CC BY-SA