How so? If I have a car lot, I'll have multiple cameras for a tiny area bumping the average camera per person without meaningful results. Sounds like the worst measurement unless you are trying to push a narrative.
>>happym+(OP)
Large parts if London are just forests, unlike Paris which is one of the densest places on earth. So of course density of population affects camera per sqm: you tend to place more cameras where there are people. This is also why I said that coverage is even a better measure: "what are the odds that I'm being filmed, now".