33. Within 21 days from the receipt of a written request from the relevant planning authority and following a complaint to the relevant planning authority from the occupant of a dwelling which lawfully existed or had planning permission at the date of this Order, the undertaker shall, at its own expense, employ an independent consultant approved by the relevant planning authority to assess the level of noise immissions from the authorised development at the complainant’s property following the procedures described in the Guidance Notes.