Section 50 Police Reform Act 2002
50 Persons acting in an anti-social manner
(1) If a constable in uniform has reason to believe that a person has been acting, or is acting, in an anti-social manner (within the meaning of section 1 of the Crime and Disorder Act 1998 (c. 37) (anti-social behaviour orders)), he may require that person to give his name and address to the constable.
http://www.legislation.gov.uk/ukpga/2002/30/section/50?view=plain
Crime and Disorder Act 1998
1 Anti-social behaviour orders.
(1) An application for an order under this section may be made by a relevant authority if it appears to the authority that the following conditions are fulfilled with respect to any person aged 10 or over, namely—
(a) that the person has acted, since the commencement date, in an anti-social manner, that is to say, in a manner that caused or was likely to cause harassment, alarm or distress to one or more persons not of the same household as himself; and
[F1(b) that such an order is necessary to protect relevant persons from further anti-social acts by him.]
http://www.legislation.gov.uk/ukpga/1998/37/section/1?view=plain
4TheRecord 