2Where immediately before the commencement of the relevant year any lands and heritages are let under a lease for a period of more than twenty-one years or, in the case of minerals, thirty-one years, then subject to the following provisions of this Schedule the rent payable under the lease in respect of that year and of any subsequent year shall be reduced by an amount which bears the same proportion to the owner's share of the rates payable in respect of the lands and heritages for the year in which this Act passed as the rent payable under the lease bears to the gross annual value of the lands and heritages for the last-mentioned year:
Provided that the foregoing provisions of this paragraph shall not apply in relation to any such lease where by virtue of the terms thereof there is not available to the lessee thereunder the right of relief against the landlord conferred by section six of the Lands Valuation (Scotland) Act, 1854.