Sch 1 para 14
The further conditions mentioned in paragraph 12 (a)(ii) above are— (a) that it is not practicable to communicate with any person entitled to grant entry to the premises . . . ; (b) that it is practicable to communicate with a person entitled to grant entry to the premises but it is not practicable to communicate with any person entitled to grant access to the material; (c) that the material contains information which— (i) is subject to a restriction or obligation such as is mentioned in section 11(2)(b) above; and (ii) is likely to be disclosed in breach of it if a warrant is not issued; (d) that service of notice of an application for an order under paragraph 4 above may seriously prejudice the investigation.