Bob Lack, Newham's head of security, is hedging his bets on which explanation is correct. He is delighted that crime in the target area has fallen and believes it could be acting as a deterrent. But he also accepts that the software still needs improving. Criminals do, it seems, have a good chance of going undetected, although not surprisingly Lack and the Metropolitan Police are reluctant to discuss this. So what was originally intended as a six-month trial has been extended, apparently indefinitely.
Lack is keen to stress the multitude of measures designed to prevent the system being abused.
The control room is closely guarded and the digitised faces of men and women in the streets are discarded as soon as the system finds no match. That information stays with the police, who will not say who is on the database or even how many offenders are included. An internal police committee chooses the list of names, which probably embraces paedophiles and drug dealers as well as violent robbers and burglars. David Holdstock, a spokesman for the Metropolitan Police, says people convicted of trivial offences, or who were not regarded as active criminals, would never go on the database. If you're innocent you have nothing to fear.