[50 Special powers of arrest.E+W+S
(1)A constable making a search of premises under the authority of a warrant under section 46 of this Act may arrest without warrant any person found on the premises whom he has reason to believe to be guilty of an offence relevant for the purposes of that section.
(2)A constable may arrest without warrant any person whom he has reasonable cause to suspect to be committing an offence under section 19, 20, 21 or 47(2) of this Act and, for the purpose of exercising the power conferred by this subsection, may enter any place.
In Scotland, this subsection shall have effect with the inclusion of a reference to an offence under section 4, 5 or 18 of this Act.
(3)A constable may arrest without warrant a person who refuses to declare his name and address when required to do so under section 48(2) of this Act, or whom he in such a case suspects of giving a false name and address or of intending to abscond.]