Proof of certain proceedings on which perjury is assigned N.I.

15.  On a prosecution—

(a) for perjury alleged to have been committed on the trial of an indictment; or

(b) for procuring or suborning the commission of perjury on any such trial;

the fact of the former trial shall be sufficiently proved by the production of a certificate containing the substance and effect (omitting the formal parts) of the indictment and trial purporting to be signed by the appropriate officer of the Crown Court without proof of the signature or official character of the person appearing to have signed the certificate.