20. The enforcement agent may enter relevant or specified premises under paragraph 14 or 15 of Schedule 12 respectively, or re-enter premises under paragraph 16 of Schedule 12, only by—
(a)any door, or any usual means by which entry is gained to the premises (for example, a loading bay to premises where a trade or business is carried on); or
(b)any usual means of entry, where the premises are a vehicle, vessel, aircraft, hovercraft, a tent or other moveable structure.