“ 13. As respects all periods of time referred to in this Schedule time shall be deemed to be of the essence of the contract PROVIDED ALWAYS that the Landlord or the Tenant may notwithstanding anything in this Schedule require the appointment of the Surveyor or any substitute Surveyor to determine the question of New Rent payable at any time after the commencement of each relevant period of years and any delay by the Landlord or the Tenant in this respect shall not deprive the Landlord or the Tenant of their respective right to have a New Rent determined by the Surveyor as set out herein.”