5.—(1) If any part of a specified work or any protective work required by the Agency is constructed otherwise than in accordance with the requirements of this Part of this Schedule, the Agency may by notice in writing require the undertaker at the undertaker’s own expense to comply with the requirements of this Part of this Schedule or (if the undertaker so elects and the Agency in writing consents, such consent not to be unreasonably withheld or delayed) to remove, alter or pull down the work and, where removal is required, to restore the site to its former condition to such extent and within such limits as the Agency reasonably requires.
(2) Subject to sub-paragraph (3) if, within a reasonable period, being not less than 28 days beginning with the date when a notice under sub-paragraph (1) is served upon the undertaker, the undertaker has failed to begin taking steps to comply with the requirements of the notice and has not subsequently made reasonably expeditious progress towards their implementation, the Agency may execute the works specified in the notice and any reasonable expenditure incurred by the Agency in so doing is recoverable from the undertaker.
(3) In the event of any dispute as to whether sub-paragraph (1) is properly applicable to any work in respect of which notice has been served under that sub-paragraph, or as to the reasonableness of any requirement of such a notice, the Agency must not, except in the case of an emergency, exercise the powers conferred by sub-paragraph (2) until the dispute has been finally determined in accordance with paragraph 12.