A lease terminable by notice after a death, a marriage or the formation of a civil partnership is not a long lease if—
Where the tenant of any property under a long lease, on the coming to an end of the lease, becomes or has become tenant of the property or part of it under any subsequent tenancy (whether by express grant or by implication of law), that tenancy is a long lease irrespective of its terms.
A lease—
is to be treated as if the term originally granted had been one exceeding 21 years.
Where a long lease—
it remains a long lease during that period.
Where in the case of a flat there are at any time two or more separate leases, with the same landlord and the same tenant, and—
there shall be taken to be a single long lease of the property comprised in such of those leases as are long leases.