Sch 18 para 2
(1) If it is shown to the satisfaction of a justice of the peace or, in Scotland, the sheriff or a justice of the peace, on sworn information in writing— (a) that there are reasonable grounds for the exercise in relation to any premises of a relevant power; and (b) that one or more of the conditions specified in sub-paragraph (2) below is fulfilled in relation to those premises, the justice or sheriff may by warrant authorise an enforcing authority to designate a person who shall be authorised to exercise the power in relation to those premises, in accordance with the warrant and, if need be, by force. (2) The conditions mentioned in sub-paragraph (1)(b) above are— (a) that the exercise of the power in relation to the premises has been refused; (b) that such a refusal is reasonably apprehended; (c) that the premises are unoccupied; (d) that the occupier is temporarily absent from the premises and the case is one of urgency; or (e) that an application for admission to the premises would defeat the object of the proposed entry. (2A) A justice of the peace may by warrant authorise an English or Welsh authorised person, designated for the purpose by the person who authorised them, to exercise the powers in section 108(4) (ka) in accordance with the warrant and, if need be, by force. (2B) The justice may do so only if satisfied that there are reasonable grounds for believing that— (a) there is material on or accessible from the premises in question which is likely to be of substantial value (by itself or together with other material) to an examination or investigation under section 108(4)(c), and (b) it is impracticable to communicate with a person entitled to grant access to it, or access to it is unlikely to be granted unless a warrant is produced. (3) ... (4) Every warrant under this Schedule shall continue in force until the purposes for which the warrant was issued have been fulfilled.