Police and Criminal Evidence Act 1984

2 Where—

(a) a document setting out the evidence which a person could be expected to give as a witness has been prepared for the purpose of any pending or contemplated proceedings ; and

(b) it falls within subsection (1) of section 68 above,

a statement contained in it shall not be given in evidence by virtue of that section without the leave of the court, and the court shall not give leave unless it is of the opinion that the statement ought to be admitted in the interests of justice, having regard—

(i) to the circumstances in which leave is sought and in particular to the contents of the statement; and

(ii) to any likelihood that the accused will be prejudiced by its admission in the absence of the person who supplied the information on which it is based.