22.—(1) Subject to paragraph (2), a Commissioner may summon any person to attend a hearing as a witness, at such time and place as may be specified in the summons, to answer any questions or produce any documents in his custody or under his control which relate to any matter in question in the proceedings.
(2) A person shall not be required to attend in obedience to a summons under paragraph (1) unless he has been given at least 14 days' notice before the date of the hearing or, if less than 14 days, has informed the Commissioner that he accepts such notice as he has been given.
(3) Upon the application of a person summoned under this regulation, a Commissioner may set the summons aside.
(4) A Commissioner may require any witness to give evidence on oath and for this purpose an oath may be administered in due form.