21.—(1) Not less than 28 days before starting the execution of any works in, on or under any land purchased, held, appropriated or used under this Order that are near to, or will or may affect any apparatus the removal of which has not been required by the undertaker under paragraph 20(2), the undertaker must submit to WPD a plan, section and description of the works to be executed. For the avoidance of doubt, if any works referred to require any diversion or require WPD to obtain any alternative rights, the undertaker shall give WPD sufficient notice to obtain any such alternative rights and shall not commence works of the type described unless or until any such alternative rights have been obtained.
(2) Those works must be executed only in accordance with the plan, section and description submitted under sub-paragraph 21(1) and in accordance with such reasonable requirements as may be made in accordance with sub-paragraph 21(3) by WPD for the alteration or otherwise for the protection of the apparatus, or for securing access to it.
(3) Any requirements made by WPD under sub-paragraph 21(2) must be made within a reasonable period beginning with the date on which a plan, section and description under sub-paragraph 21(1) are submitted to it.
(4) If WPD in accordance with sub-paragraph 21(3) and in consequence of the works proposed by the undertaker, reasonably requires the removal of any apparatus and gives written notice to the undertaker of that requirement, paragraphs 16 to 20 apply as if the removal of the apparatus had been required by the undertaker under paragraph 20(2)).
(5) Nothing in this paragraph precludes the undertaker from submitting at any time or from time to time, but in no case less than the reasonable period provided for in sub-paragraph 21(3) before commencing the execution of any works, a new plan, section and description instead of the plan, section and description previously submitted, and having done so the provisions of this paragraph apply to and in respect of the new plan, section and description.
(6) The undertaker is not required to comply with sub-paragraph 21(1) in a case of emergency but in that case it must give to WPD notice as soon as is reasonably practicable and a plan, section and description of those works as soon as reasonably practicable subsequently and must comply with sub-paragraph 21(1)) in so far as is reasonably practicable in the circumstances.