11. Where in consequence of the proposed construction of any of the authorised works, the Agency or the specified undertaker requires the removal of apparatus under paragraph 5(1) or the specified undertaker makes requirements for the protection or alteration of apparatus under paragraph 7(2), the Agency 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 works and the specified undertaker must use all reasonable endeavours to co-operate with the Agency for that purpose.