The vast, vast majority of the 600k (methodology is questionable) cameras in London are private indoor CCTV cameras that don't monitor public areas. TFA appear

The vast, vast majority of the 600k (methodology is questionable) cameras in London are private indoor CCTV cameras that don't monitor public areas. TFA appears to be about government-operated cameras in public areas. Comparing those two figures is apples to oranges. That's not to say London doesn't have significant government operated camera installations. Most are road cameras used to optimise traffic light patterns, but there is also the "Ring of Steel" in the City of London which, at ~650, is probably the largest integrated surveillance camera installation in London.