Document not to be retained if photograph or copy sufficient
38Where a document delivered to an officer of the Board under this Part of this Schedule is of such a nature that a photograph or copy of it would be sufficient—
(a)for use as evidence at a trial for an offence, or
(b)for forensic examination or for investigation in connection with an offence,
it shall not be retained longer than is necessary to establish that fact and to obtain the photograph or copy.