Testator

Testamentary capacity is the legal test from Banks v Goodfellow (1870): you must understand the nature of making a will, the extent of your estate, the claims of those you might benefit, and have no disorder of the mind affecting these.

Capacity can fluctuate — a will signed during a lucid interval can be valid even if dementia is later diagnosed. Solicitors often obtain a contemporaneous medical opinion ('the golden rule') for elderly or vulnerable testators.