A public inquirer may, at a hearing of a public inquiry, take evidence on oath or affirmation and for that purpose--
(a) the public inquirer may require a person appearing at the hearing to give evidence either to take an oath or to make an affirmation in a form approved by the public inquirer, and
(b) the public inquirer, or any other person authorised by the public inquirer, may administer an oath or affirmation to a person so appearing at the hearing.