18.—(1) Subject to the provisions of this regulation, the tribunal may admit as evidence a witness statement of a proposed witness supplied under regulation 9(4) or (8), notwithstanding that he is not to be called as a witness at the hearing.
(2) Evidence shall not be admissible under this regulation if it would not have been admissible had it been given orally.
(3) For the purposes of this regulation, a written statement purporting to be made and signed by a person and witnessed by another person shall be presumed to have been made by that person unless the contrary be shown.
(4) Nothing in this regulation shall prejudice the admission of written evidence which would be admissible apart from the provisions of this regulation.