“(1) A term of a lease of premises that consist of or include a dwelling is of no effect so far as the term makes provision (however expressed) requiring a tenant under that or any inferior lease to—

(a) prohibit a sub-tenant under a relevant tenancy or regulated tenancy from having a child live with or visit them at the dwelling, or

(b) restrict the circumstances in which a sub-tenant under a relevant tenancy or regulated tenancy may have a child live with or visit them at the dwelling.

(2) Subsection (1) does not apply if—

(a) the provision is a proportionate means of achieving a legitimate aim, or

(b) the landlord under the lease or a superior landlord is insured under a contract of insurance—