London cops have been given the power to "disperse" anyone under 16, gathered in groups of two or more, from almost all of central London, after 9PM. The police don't have to see the kids doing anything wrong, they only have to believe "the presence or behaviour of a group of two or more persons in any public place in the relevant locality has resulted, or is likely to result, in any members of the public being intimidated, harassed, alarmed or distressed."
If you're observant, in central London, you may have seen this notice casually cable-tied to a lamppost. From afar, it looks like a council planning application, or parking bay suspension. It's actually notifying you that you're now subject to an anti-social behaviour order, and the Police (and the not-really-Police Community Support Officers) have special powers to remove you from this area if they feel like it. These dispersal areas cover large swathes of London, and other cities in England. There are now over 1000 such areas.
It's ambiguously worded, but it institutes law that in other words may not seem so palatable. There's a curfew for unsupervised under-16s, from 9pm to 6am. Any group of 2 or more people can be broken up and/or that the member of the group have to leave the designated area (if they do not live there). Crucially, police do not have to see actual anti-social behaviour, but a constable in uniform has reasonable grounds for believing that the presence or behaviour of a group of two or more persons in any public place in the relevant locality has resulted, or is likely to result, in any members of the public being intimidated, harassed, alarmed or distressed…