ernesto
Quite simple really, it's a common law obligation on everyone in the UK to prevent crime. In fact the Police only came into being because in the main then, as now, the great British public abdicated the responsibility.
If you're asking where it written into legislation, it's not, it's common law. But if you're asking that question, you should also ask what right do you have to take photos? In legislation, none at all. However, like the right to question what you're doing there's nothing stopping you.
As I've said before there is no such 'right', it's the exact opposite ie there's no law stopping you... yet.
Do I think one will come? yes, I think there will be at some point stopping you photographing a person without their consent. That's an unfortunate by product of the internet, where you can publish what you want. Will I agree with that? In some circumstances yes, in others no. But either way, the attitude of some on here, as always isn't going to help. However, there's no point in trying to shoot me because you, and some others don't like the message, you'd be better off trying to get a code of conduct for photographers put together and forestall legislation.
