A question is a dwellinghouse never lived in bought by an investor with no intention of living in it really C3.
All of the sub categories of C3 refer to people actually ‘living’ there.
The question is pertinent because of the blight of what Peter Rees memorably calls ‘safe deposit box’ housing. Such units are effectively removed from the housing stock, and unable to meet need. People must cram into the remaining dwelling stock. It is the same as if it didnt exist. How then can it meet a supply and how then can the presumption on favour of housing apply?
Unfortunately the law is not on the side of such simple verbal logic. The courts have held in Moore v. SSCLG  that
there is no requirement that before a building can be described as a dwellinghouse it must be occupied as a permanent home.
This begs the question – can a condition precedent be used?
This has difficulties as these normally state cannot commence until or cannot be occupied until.
But guidance is very clear.
Such conditions should only be used where the local planning authority is satisfied that the requirements of the condition (including the timing of compliance) are so fundamental to the development permitted that it would have been otherwise necessary to refuse the whole permission.
And here it would be to ensure it is lived in to meet the need for places to live, not for empty safety deposit boxes, which are collectibles and serve no need.
I suggest a simple condition precedent.
The development shall not commence or continue in a state of non permanent occupancy for a continuous period of six calender months or greater. In which case this consent will not commence or will cease (as appropriate). A state of non-permanent occupancy is defined as a condition where no-one is living at the property as their main place of residence. This condition shall not apply during a period of mortagee in possession until the property is then sold on or let by a mortgagee in possession.
Reason: To ensure the property is lived in to meet the need for places to live as set out in the development plan, the London Plan and National Planning Policy.
This avoids I think the very complicated S106 based approach of Islington – Lawyers?
Note Boris’s defense that this is needed for regeneration is preposterous as all it does is push land prices up to bubble levels which will wreck regeneration.