law: 20. Sub-tenant to become tenant on determination of tenancy.-
  Where the interest of a tenant of any premises is determined for any reason, any sub-tenant to whom the whole or any part of such premises has been lawfully sub-let whether before or after the commencement of this Act shall, subject to the provisions of this Act, be deemed to become the tenant of the landlord on the same terms and conditions on which he would have held from the tenant if the tenancy had continued.