Claim for specific performance of a 15 years lease agreement - Claimant's interim application for injunctive relief - Rent Restriction Act - Certificate of exemption - Notice to quit occupation of premises - Failure on the part of the tenant to pay rent when due - Whether notice to quit is valid - Presuption against retrospective operation of legislation - Undertaking as to damages - Failure of claimant to provide undertaking as to damages - Failure of defendnat to provide any undertaking.