7.—(1) An application to the Tribunal by a person or organisation to be made a party to a reference or an application referred to in rule 3 may be made by serving on the Secretary, within the time specified under rule 5(2)(c), a notice of intervention in Form 5, together with a statement of his interest:
Provided that the Tribunal or the Chairman may give leave, subject to such conditions as the Tribunal or Chairman may think fit, to serve such notice notwithstanding the expiration of the time specified under that rule.
(2) As soon as practicable after receipt of a notice served under this rule the Secretary shall–
(a)serve a copy of the notice on every other party to the proceedings, and
(b)serve on the intervener a copy of the applicant’s reference or application and statement of case, together with any other notice of intervention which has been served upon him.