There are two housing acts which have some effect, the 1985 and 1988 acts. D had the benefit of the property transferred to him by C as a result of a consultation process in which A took part. In order for the transfer to take place a majority of tenants had to vote yes. This led to a tenancy agreement which gave B rights in the event of A's death and so had provisions in it made with B specifically in mind. These terms are above and beyond the statutory rights under the 1988 act which then governed most of the provisions of the tenancy. So in that sense no D is not justified under the housing act.

Kind regards

Benedict White