A number of issues can arise on death. They may relate to a person's capacity when they executed their last will or whether they were unduly influenced when they made their last will. If a will was made by a person who suffered dementia for example, their last will is invalid and a previous will may apply. Equally if they were under the undue influence of an other, any gift to that person will be deleted in the will.
The deceased person may also have failed to properly recognise a family member entitled to a claim against their estate. This person may have a claim under the Family Protection Act, or if they were a partner, the Property (Relationships) Act. Even if you are not entitled to claim under either of the above two Acts you may have a claim because the deceased promised to leave you something in return for services you provided.
If the deceased failed to leave you the asset as promised, even though you provided the services, you may have a claim under the Testamentary Promises Act.