If any person having a lease of any portion of the said land from the Governor or the Minister aforesaid, or from an intermediate lessee, shall be desirous of erecting or extending any buildings or improvements upon any part thereof, and the term of his present lease shall not in the opinion of the Board be such as to justify him in carrying out his intended buildings or improvements, the Board may, with the consent of the Governor, agree with such lessee upon condition that he shall forthwith effect such extension for an extended lease of the whole or a part of the land held by him for any term not exceeding twenty-one years; and such extended lease may contain a provision for the payment to the lessee upon the determination by effluxion of time of his lease by the Board or the incoming lessee of the value of improvements, erected during the term of such extended lease. The annual rent to be received for any such renewal lease shall not be less than ten dollars per centum upon the capital value of the land without the buildings or improvements belonging to the lessee; and such lease shall contain such covenants, conditions, and agreements as may be approved between the Board and such lessee.