Dilemna
On the horns here, unlike speed cameras the ANPR cameras identify significant events.
With the speed cameras there is no allowance for circumstances and before I get flamed, most speed limits are based on worst-case scenarios ie rush hour or school-run levels of activity. There are a very large number of dual carriageways with 50mph or less limits which can be safely navigated at higher speeds in the dead of night for example. A 'copper in a car' is likely to apply the attitude test to someone doing 56mph on a 50mph section at 3am on a dry road whilst the camera just says 'That'll be £100 - or whatever the going rate is'.
If someone is driving around with no insurance etc then I don't want to be in the same vicinity and the best way is for them to be taken off the road. These are people who know full well that in the past their chances of being caught were minimal so why not. They can't be arsed to buy insurance etc (assuming they are not banned and so should not be on the road anyway) which means that when they are involved in an 'unintended occurence' the other drivers get hammered with all the consequences of delays getting things sorted and costs such as their excess.
On balance, I think I would prefer that the police could keep ANPR locations secret despite the 'nothing to hide etc etc' mob rather than in support of them.