s 161 Entry and search of premises for purposes of arrest
(1) This section applies if a constable has power to arrest a person under an extradition arrest power. (2) A constable may enter and search any premises for the purpose of exercising the power of arrest if he has reasonable grounds for believing that the person is on the premises. (3) The power to search conferred by subsection (2) is exercisable only to the extent that is reasonably required for the purpose of exercising the power of arrest. (4) A constable who has entered premises in exercise of the power conferred by subsection (2) may seize and retain anything which is on the premises if he has reasonable grounds for believing— (a) that it has been obtained in consequence of the commission of an offence or it is evidence in relation to an offence, and (b) that it is necessary to seize it in order to prevent it being concealed, lost, damaged, altered or destroyed. (5) An offence includes an offence committed outside the United Kingdom. (6) If the premises contain 2 or more separate dwellings, the power conferred by subsection (2) is a power to enter and search only— (a) any parts of the premises which the occupiers of any dwelling comprised in the premises use in common with the occupiers of any other dwelling comprised in the premises, and (b) any dwelling comprised in the premises in which the constable has reasonable grounds for believing that the person may be.