13. Where in consequence of the proposed construction of any of the authorised development, the undertaker or a statutory undertaker requires the removal of apparatus under paragraph 6(2) or a statutory undertaker makes requirements for the protection or alteration of apparatus under paragraph 8 or 9, the undertaker must use its best endeavours to co-ordinate the execution of the works in the interests of safety and the efficient and economic execution of the authorised development and taking into account the need to ensure the safe and efficient operation of the statutory undertaker’s undertaking, and the statutory undertaker must use its best endeavours to co-operate with the undertaker for that purpose.