ShesGot it's in the CAL book. She doesn't really clarify it till nearer to the end but if you're reading an ebook then you can search 'tenancy' and it brings it up. White house farm was owned by a trust. Nevill was the tenant (even though he did own other land, cottages and buildings).
JB tried to keep the tenancy after the murders but had to apply to the trustees. Ann applied for it too, and the trustees decided it should go to Ann. Ann's brother said that Ann's husband wanted more land to farm and Ann wanted a bigger house so it suited them from a practical pov.
The gran (June and Pamela's mum) owned and lived at Vaulty when the murders took place and then left everything to Pamela (Ann's mum).
Before the murders, apparently JB loved Vaulty and he hoped to inherit it and live there. (It is a beautiful building and setting). It was one of the many areas, him and Ann were in competition.