What happens when the 5 year lease term expires?

On the expiry of the first 5 year term, the tenant shall have the option of renewal of the lease agreement on the same conditions of the original lease, with the exception of the rent, which shall be increased in accordance with an ad-hoc valuation to be carried out by a Government appointed architect at the time of renewal, so however that such increase shall not be less than that reflected in the Index of Inflation.