21.—(1) No person shall obstruct or impede an Inspector or any person acting under the authority of the Minister or the Chief Inspector in the exercise of any rights, powers or duties under this Order.
(2) No person shall without reasonable excuse and after having had the expenses (if any) to which he is entitled tendered to him, fail to comply with any summons of —
(a)
an investigator-in-charge carrying out an investigation under this Order; or
(b)
any person empowered to exercise the powers of the investigator-in-charge under paragraph 9(4).
(3) The onus of proving reasonable excuse for failing to comply with a summons shall lie on the person relying on such excuse.