The second development whilst away is that of Spencer v Taylor  EWCA 1600 which has had permission to appeal to the Supreme Court refused.
Therefore, the decision stands and where an assured shorthold tenancy was a fixed term and then a statutory periodic tenancy arises after the fixed term tenancy has ended, a section 21(1)(b) notice is sufficient which is just 2 clear months in writing with no need to expire on any particular day.
Spencer does not apply where the tenancy was periodic from the outset (commonly found with a verbal tenancy) and it probably does not apply to a tenancy which continues as a contractual periodic tenancy at the end of the initial term instead of ending. In these cases (including with our tenancy agreements) the old advice remains and a 21(1)(b) notice should be served during the fixed term and a 21(4)(a) should be served during the periodic part of the tenancy.
To avoid confusion, landlords could continue serving a section 21(4)(a) in all periodic cases if convenient (this depends on timing a little) because Spencer does not outlaw it’s usage even where the tenancy is statutory periodic. However, if a 21(4)(a) notice has been done wrongly, Spencer will in most cases (where the tenancy is statutory periodic) ensure the notice is valid regardless of the date of expiry.