a landlord owns a commercial premises and their tenant is leasing the premises for 12 years. the tenant decides to sublet for a part of the term of years left on the lease and now becomes the ‘sub-lessor’. the head landlord remains safe as the new tenant (the ‘sub-lessee’) is liable to the outgoing tenant (the ‘sub-lessor’) and the outgoing tenant remains liable to the head landlord. first, you should get details of the proposed new tenant.