Re: Keeping pace?
It is invasive to obtain an official copy of a person's fingerprints, you need to coat their hands in ink and press them to a piece of paper (or similar). That is why they need to obtain permission. The police can of course freely take a copy of latent prints (the mark you leave behind) at crime scenes.
The same can be said of DNA evidence.
Taking someone's photograph in public is not invasive and permitted by any photographer.
Just as ANPR can record the presence of a number-plate to record a crime or just presence its the processing of the sequence of ANPR records to trace a car's journey that is different and questionable. We need to limit the processing of the data not the capture.