Does one cease to be protected under the protection from eviction act 1977 if one has voluntarily given formal notice to a landlord of one's intention to vacate by a certain date but then fails to do so due to whatever circumstances?
A tenant is protected by the PfEA - but if the tenancy has ended, and unless the former tenant and landlord agree otherwise, the former tenant becomes a trespasser.
While this may give the impression that the former tenant is no longer protected, evidence suggests that that is not, in fact, the case.
On ending and resurrecting the tenancy, and charging extra, The Landlord Law Blog states:
My understanding is that if the tenant serves a proper notice to quit, then that will end the tenancy. I am not aware of any rules saying that it can be retracted. (Although you can resurrect the tenancy by accepting rent without qualifying that it is accepted as ‘mesne profits‘.)
There is also the very old rule in the Distress for Rent Act 1737 which I discuss here which says that where a tenant gives notice to quit but then fails to move out, the landlord is entitled to charge double rent.
Despite that, discussion in the comments following this article about deeds of surrender (including from the author of the article quoted above) appear to suggest that if an occupant stays in a property after their tenancy has ended, the PfEA may still apply - and hence the safest way to evict them is via a court (assuming they don't leave voluntarily).
Indeed, the Civil Procedure Rules for possession claims specifically exclude these circumstances in their definition of "possession claim against trespassers", suggesting that a claim should be treated as if the occupants were tenants:
‘a possession claim against trespassers’ means a claim for the recovery of land which the claimant alleges is occupied only by a person or persons who entered or remained on the land without the consent of a person entitled to possession of that land but does not include a claim against a tenant or sub-tenant whether his tenancy has been terminated or not;
More realistically, if the tenant needs to delay their departure by a few days, it's best to try and come to an agreement with the landlord.
I have it on good authority that these two instruments differ in nature slightly. A tenant's NTQ which has fully come to term is the equivalent in effect to a matured s21 notice by the landlord and it seems like the landlord can take that to a court for a possession hearing. The deed of surrender however as something signed and executed by both parties with mutual agreement rather than something served by one party upon another is more equivalent to a judicial order for possession and only needs a warrant for enforcement by the bailiffs but it still doesn't entitle the landlord to change the locks. According to this solicitor, an NTQ that isn't then honoured may be dealt with as a breach of lease by serving a section 8 notice on corresponding grounds.