—(1) Where the plaintiff in a probate action disputes the interest of a defendant he must allege in his statement of claim that he denies the interest of that defendant.
(2) In a probate action in which the interest by virtue of which a party claims to be entitled to a grant of letters of administration is disputed, the party disputing that interest must show in his pleading that if the allegations made therein are proved he would be entitled to an interest in the estate.
(3) Without prejudice to Order 18, Rule 7, any party who pleads that at the time when a will, the subject of the action, was alleged to have been executed the testator did not know and approve of its contents must specify the nature of the case on which he intends to rely, and no allegation in support of that plea which would be relevant in support of any of the following other pleas, that is to say:
that the will was not duly executed;
that at the time of the execution of the will the testator was not of sound mind, memory and understanding; and
that the execution of the will was obtained by undue influence or fraud,
shall be made by that party unless that other plea is also pleaded.