Number of CCTV cameras
According to a 2011 Freedom of Information Act request, the total number of local government operated CCTV cameras in the City of London was 649.
The number of surveillance cameras that are part of the TEZ is often wrongly quoted as 500,000. This figure relates to Greater London, which has an area of 1,572 square km compared with the 3 square km of the City of London that the ring of steel covers. Furthermore, it has been acknowledged for several years that the methodology behind this figure is flawed, but it has been widely quoted.
The figure of 500,000 comes from a study by Michael McCahill and Clive Norris of UrbanEye published in 2002. Based on a small sample in Putney High Street, McCahill and Norris extrapolate the number of surveillance cameras in Greater London to be 500,000 and in the United Kingdom to be 4.2 million. More reliable estimates put the total number of private and local government surveillance cameras in the whole of the United Kingdom at around 1.85 million in 2011.