A district judge or registrar may require an affidavit or a witness statement from any person he may think fit for the purpose of satisfying himself as to any of the matters referred to in rules 13, 14 and 15, and in any such affidavit sworn or witness statement made by an attesting witness or other person present at the time of the execution of a will the deponent must depose to, or the maker of the witness statement must give evidence of, the manner in which the will was executed.