The validity of
anything done by or in relation to a person purporting to act in the office of
Inspector under an appointment made under section 11 or 12 cannot
be called in question on the ground that —
(a) the
occasion for the appointment had not arisen;
(b)
there is a defect or irregularity in the appointment;
(c) the
appointment had ceased to have effect; or
(d) the
occasion for the person to act had not arisen or had ceased.