s 7
(1) An assured tenancy which— (a) is granted to a person (alone or jointly with others) who, immediately before the tenancy was granted, was the tenant (or, in the case of joint tenants, one of the tenants) under an assured tenancy other than a shorthold tenancy (“the old tenancy”), (b) is granted (alone or jointly with others) by a person who was at that time the landlord (or one of the joint landlords) under the old tenancy, and (c) is not one in respect of which a notice is served as mentioned in sub-paragraph (2) below. (2) The notice referred to in sub-paragraph (1)(c) above is one which— (a) is in such form as may be prescribed, (b) is served before the assured tenancy is entered into, (c) is served by the person who is to be the tenant under the assured tenancy on the person who is to be the landlord under that tenancy (or, in the case of joint landlords, on at least one of the persons who are to be joint landlords), and (d) states that the assured tenancy to which it relates is to be a shorthold tenancy.