Renewal of leased hold land

MY GRANDFATHER HAD TAKEN A LAND ON LEASE THROUGH LEASE DEED IN 1954. LEASE PERIOD WAS FOR 50 YEARS AND EXTENSION OF 10 YEARS AS MENTIONED IN LEASE DEED. A BUILDING HAVE BEEN CONSTRUCTED ON LEASE HOLD PROPERTY. AT PRESENT TENANTS HAVE OCCUPIED THE FLATS. NOW I WANT TO EXTEND THE LEASE BUT THE LANDLORD IS NOT WILLING TO EXTEND. WHAT WILL BE THE PROCEDURE TO EXTEND LEASE.