It is essential to the exercise of such a power that a testator shall understand the nature of the act and its effects; shall understand the extent of property of which he is disposing to which he ought to give effect; and with a view to the latter object, that no disorder of the mind shall poison his affections, pervert his sense of right, or prevent the exercise of his natural faculties - that no insane delusion shall influence his will in disposing of his property and bring about a disposal of it which, if the mind be sound, would not have been made.

Banks v Goodfellow(1870) LR 5 QB 549 per Cockburn J at 565

Critically discuss this statement.