2.—(1) Subject to paragraph (2), the notice of appeal shall be sent to the Secretary within 21 days from the date of the service on the appellant of the notice appealed against.
(2) A tribunal may extend the time mentioned in paragraph (1) where it is satisfied, on an application made in writing to the Secretary either before or after the expiration of that time, that it is not or was not reasonably practicable for an appeal to be brought within that time.