Not later than the beginning of the tenancy the landlord (or, where there are joint landlords, any of them) gave notice in writing to the tenant that possession might be recovered on this Ground or the sheriff is of the opinion that it is reasonable to dispense with the requirement of notice and (in either case)—
(a)at any time before the beginning of the tenancy, the landlord who is seeking possession or, in the case of joint landlords seeking possession, at least one of them occupied the house as his only or principal home; or
(b)the landlord who is seeking possession or, in the case of joint landlords seeking possession, at least one of them requires the house as his or his spouse’s only or principal home, and neither the landlord (or, in the case of joint landlords, any one of them) nor any other person who, as landlord, derived title from the landlord who gave the notice mentioned above acquired the landlord’s interest in the tenancy for value.